

EXHIBIT 10.15


[*] -- Certain information omitted and filed separately with the Commission
pursuant to a confidential treatment request under Rule 24b-2 of the Commission.

                                 THIRD AMENDMENT
                              TO PURCHASE AGREEMENT

THIRD AMENDMENT (this "Amendment"), dated and effective as of the 8th day of
September, 1998 (the "Effective Date"), to the PURCHASE AGREEMENT dated
September 6, 1996 , as amended by the FIRST AMENDMENT dated April 22, 1997 and
by the SECOND AMENDMENT dated December 9, 1997 (as thus amended, the "Purchase
Agreement" or "Agreement"), between CREE RESEARCH, INC. ("Seller"), a
corporation organized under the laws of the State of North Carolina, the United
States of America, and SIEMENS AKTIENGESELLSCHAFT ("Purchaser"), a corporation
organized under the laws of the Federal Republic of Germany. As used in this
Amendment, capitalized terms not defined herein which are defined in the
Purchase Agreement shall have the meaning defined in the Purchase Agreement.

In consideration of the mutual provisions below the parties hereby agree as
follows:

1.    The first "Whereas" clause of the Purchase Agreement is amended by adding
      the phrase "and silicon carbide (SiC) wafers" immediately after "LED's in
      die form". The second "Whereas" clause of the Purchase Agreement is
      amended by adding the phrase "and SiC wafers" immediately after "LED die
      products". The third "Whereas" clause of the Purchase Agreement is amended
      by adding the phrase "and wafers" immediately after "such LED's".

2.    Section 1.2(d) of the Purchase Agreement is amended to read as follows:
      "'Products' mean LED chips and silicon carbide substrates which conform to
      the applicable Product Specifications. Products supplied under this
      Agreement will be 'GaN LEDs,' '[*] LEDs' and 'SiC Wafers' as described in
      Schedule 3. 'GaN LEDs' means LED die incorporating gallium nitride
      materials and a conductive buffer layer on SIC Wafers. '[*] LEDs' means
      LED die incorporating [ * ] and a conductive buffer layer on SIC Wafers.
      'SiC Wafers' mean silicon carbide substrates."

3.    The Purchase Agreement is amended by replacing First Amended Schedule 1
      and Supplement No. 1 to Schedule 1 in their entirety with the Second
      Amended Schedule 1 annexed hereto.

4.    The Purchase Agreement is amended by replacing First Amended Schedule 2
      and Supplement No. 1 to Schedule 2 in their entirety with the Second
      Amended Schedule 2 annexed hereto.

5.    The Purchase Agreement is amended by replacing the Second Amended Schedule
      3 in its entirety with the Third Amended Schedule 3 annexed hereto.

6.    Second Amended Schedule 1, Second Amended Schedule 2 and Third Amended
      Schedule 3 shall apply to all Products scheduled to be shipped on and
      after June 29, 1998 and, with respect to such products, supersedes the
      respective Schedules of the Purchase Agreement as previously amended.  The
      Purchase Agreement, as previously amended, shall govern the prices and
      other terms applicable to Products scheduled to be shipped prior to June
      29, 1998; such prices are final and no adjustment is made by this
      Amendment.  The Purchase Agreement, as amended hereby, supersedes Article
      7 of the Development, License and Supply Agreement between the parties
      dated October 25, 1995 with respect to all Products purchased or to be
      purchased under this Purchase Agreement.

7.    Seller and Purchaser will continue to work to improve the ESD sensitivity
      of the LED Products with the goal developing a mutually acceptable
      improvement with a minimum RAET rating of [ * ] (as


<PAGE>

      measured using the RAET method described in the Product Specifications
      contained in Third Amended Schedule 3).

8.    Except as amended hereby, the terms and conditions of the Purchase
      Agreement shall continue in effect.

IN WITNESS WHEREOF, the parties, through their respective duly authorized
officers, have executed this Amendment to be effective as of the Effective Date
set out in the preamble hereto.

CREE RESEARCH, INC.                 SIEMENS AKTIENGESELLSCHAFT



By     /s/ F. Neal Hunter           By   /s/ R. Mueller
     -------------------------           ---------------------------------------
     F. Neal Hunter, President           R. Mueller, President, Opto
                                         Semiconductors

Date    9/8/98                      Date       9/16/98
     -------------------------           ---------------------------------------


                                    By   /s/ C. Hagen
                                         ---------------------------------------
                                         C. Hagen, Vice President-Finance &
                                         Admin.

                                    Date      9/16/98
                                         ---------------------------------------


                                     Page 2



<PAGE>


                            SECOND AMENDED Schedule 1

                         Quantity and Shipment Schedule

A.    Quantity Commitment.

      1.    During the period commencing [ * ] and ending [ * ] Purchaser will
            purchase from Seller the quantities of each Product type shown
            below:

            GaN LEDs             [ * ]
            [ * ] LEDs           [ * ]
            SiC Wafers           [ * ]

            Purchaser may submit orders for additional Product quantities to be
            delivered during such period. Subject to available capacity and
            mutual agreement as to the applicable terms and conditions, Seller
            will use all commercially reasonable efforts to supply such
            additional quantities.

      2.    If and to the extent the quantity of [ * ] LEDs Purchaser requires
            for the manufacture of LED products during the period from [ * ]
            through [ * ] is less than [ * ] and subject to Paragraph (B)(1)
            below, Purchaser may elect to purchase GaN LEDs in lieu of [ * ]
            LEDs, at the prices stated for GaN LEDs under this Agreement,
            provided that Purchaser gives Seller written notice of such election
            at least ninety (90) days in advance of the scheduled shipping date.

B.    Shipment Schedule.

      1.    The shipment schedule for units to be shipped under this Schedule
            during the period ending [ * ] is as follows:

            ------------------------------------------------------------------
                                       Quarterly (13-Week) Period Ending
                                   -------------------------------------------
                   Product*           [ * ]      [ * ]     [ * ]     [ * ]
            =============================================---------------------
            GaN LED die (in K)      [ * ] **     [ * ]     [ * ]     [ * ]
            ------------------------------------------------------------------
            ------------------------------------------------------------------
            [ * ] LED die (in K)      [ * ]      [ * ]   [ * ] *** [ * ] ***
            ------------------------------------------------------------------
            ------------------------------------------------------------------
            SiC Wafers                [ * ]      [ * ]     [ * ]     [ * ]
            ------------------------------------------------------------------

            *  As described in Third Amended Schedule 3.
            **  [ * ]  was included in [ * ] shipments.
            *** Seller acknowledges that Purchaser's customers have not yet
            qualified any [ * ] LEDs manufactured by Seller. Purchaser will use
            all reasonable efforts to obtain such qualification in order that
            its volume requirements for the periods noted equal or exceed the
            quantities listed above. In the event Purchaser is unable to obtain
            such qualification, it may elect to purchase GaN LEDs in lieu of
            [ * ] LEDs under the terms and conditions of Paragraph (A)(2).

      2.    Subject to the provisions of this Agreement, unless otherwise
            mutually agreed the quarterly amounts shown above will be shipped in
            three approximately equal shipments on the last day of the fourth,
            eighth and final week of each quarterly period, except that the
            [ * ] LEDs scheduled for delivery during the first quarterly period
            shall be shipped the last week of such period.  Purchaser may
            without charge reschedule shipments of quantities of GaN LEDs shown
            above under the following terms:

                                     Page 3
<PAGE>

            (a)   for quantities scheduled to be shipped more than twenty-four
                  (24) weeks following Seller's receipt of written notice from
                  Purchaser requesting rescheduling, Purchaser may reschedule up
                  to thirty percent (30%) of such quantity for up to ninety (90)
                  days after the originally scheduled shipment date but not
                  later than [ * ]; and

            (b)   for quantities scheduled to be shipped more than twelve (12)
                  weeks but within twenty-four (24) weeks following Seller's
                  receipt of written notice from Purchaser requesting
                  rescheduling, Purchaser may reschedule up to ten percent (10%)
                  of such quantity for up to ninety (90) days after the
                  originally scheduled shipment date but not later than [ * ].

            In all other cases Purchaser may reschedule shipments only with
            Seller's mutual written agreement. Purchaser's notice requesting
            rescheduling must specify the quantity to be deferred and the date
            on which shipment is to be made. Subject to the foregoing, a
            shipment may be rescheduled any number of times under this
            paragraph.

C.    Purchase Orders.

      1.    Purchaser will submit written purchase orders evidencing its
            commitment to purchase Products under this Schedule  prior to each
            scheduled shipment date. Purchase orders will specify the particular
            quantity of each Product type to be shipped.  Prior to or
            concurrently with the execution of the amendment to which this
            Schedule is annexed, Purchaser has delivered or will deliver its
            purchase order to Seller for the quantities to be shipped during the
            first quarterly period shown in Paragraph (B)(1) above.  All other
            purchase orders must be received at least forty-five (45) days prior
            to the calendar quarter in which shipment is scheduled.

      2.    Such purchase orders may be submitted through Purchaser's offices in
            Regensburg, Germany, or through any other Siemens Semiconductor
            location authorized by Purchaser.  In the event Purchaser requests
            delivery of shipments to a Siemens Semiconductor location other than
            Regensburg, Germany, Purchaser's personnel at such location shall be
            authorized to act on Purchaser's behalf with respect to scheduling
            and acceptance of shipments and other matters relating thereto.  The
            terms and conditions of this Agreement shall govern the purchase of
            Products hereunder notwithstanding any contrary provisions of any
            purchase order, order acknowledgment or other similar document
            issued by either party.  Purchase orders issued under this Agreement
            are intended as an administrative convenience and, in the case of
            [ * ] Products, to specify the selection of such Products, but the
            obligation to purchase Products under this Agreement is not
            conditioned upon issuance of a purchase order.




                                     Page 4
<PAGE>




                            SECOND AMENDED Schedule 2

                           Price and Payment Schedule


A.    Prices.

      1.    Prices of Products purchased under Second Amended Schedule 1 shall
            be determined as follows, subject to Paragraph (A)(2) of this
            Schedule:

            GaN LEDs:

                   -------------------------------------------
                    Incremental Quantities   Unit Price (US$)
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------

            [ * ] LEDs:

                   -------------------------------------------
                    Incremental Quantities   Unit Price (US$)
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------

            SiC Wafers:

                   -------------------------------------------
                    Incremental Quantities   Unit Price (US$)
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------
                   -------------------------------------------
                             [ * ]                [ * ]
                   -------------------------------------------

                   The reduction in per unit prices reflects Seller's
            expectation that it will improve manufacturing yields and reduce per
            unit cost

      2.    Purchaser and Seller will share the risk of currency exchange rate
            fluctuations, as provided in this paragraph, for units shipped
            pursuant to Second Amended Schedule 1.  The unit price for such
            shipments shall be adjusted by the applicable percentage below
            according to the value of the "DM-Dollar Exchange Rate" on the
            shipment date.  For purposes of this paragraph, the "DM-Dollar
            Exchange Rate" means the average of the foreign exchange selling
            rates for German Marks per U.S. Dollar, as published in the Wall
            Street Journal during the thirty (30) calendar days preceding the
            date of shipment, for rates quoted in New York the preceding
            business day for trading among banks in amounts of $1 million or
            more.


                                     Page 5
<PAGE>

             ---------------------------------------------------------------
                                                    Percentage Price
             DM-Dollar Exchange rate                Adjustment
             ---------------------------------------------------------------
             Equal to or greater than 2.0
             Equal to or greater than 1.9 and less
             than 2.0                                        [ * ]
             Greater than 1.6 and less than 1.9              [ * ]
             Equal to or less than 1.6 and greater           [ * ]
             than 1.5                                        [ * ]
             Equal to or less than 1.5                       [ * ]
             ---------------------------------------------------------------

B.    Payment Terms.

      Products will be invoiced upon shipment. Invoices shall be due and payable
      within twenty (20) days from the invoice date.





                                     Page 6
<PAGE>




                            THIRD AMENDED Schedule 3

                             Product Specifications


A.    GaN LEDs.

      Product Specifications for GaN LEDs purchased under this Agreement are set
      forth in Attachment A hereto.

B.    [ * ] LEDs.

      Product Specifications for [ * ] LEDs purchased under this Agreement shall
      be Seller's published specifications applicable to such Products as and
      when the same are made generally available to Seller's customers, except
      that for purposes of this Agreement the minimum specifications shall be as
      follows:

      1.    Brightness, forward voltage and dominant wavelength (measured in the
            same manner as specified for GaN LEDs in Attachment A):

            -------------------------------------------------------------------
                                                 Forward         Dominant
            Description       Brightness         Voltage        Wavelength
                         ------------------------------------
                           Typ.       Min.     Typ.   Max.
            -------------------------------------------------------------------
            Green          [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
            -------------------------------------------------------------------
            -------------------------------------------------------------------
            Blue           [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
            -------------------------------------------------------------------
            -------------------------------------------------------------------
            Signal Green   [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
            -------------------------------------------------------------------
            -------------------------------------------------------------------
            "GM" Blue      [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
            -------------------------------------------------------------------

      2.    [ * ] LEDs shall have a minimum electrostatic discharge (ESD)
            threshold of [ * ] (HBM), as measured by the RAET method described
            in Note 2 to Attachment A. Seller shall use commercially reasonable
            efforts to improve the ESD resistivity of [ * ] LEDs to a target of
            [ * ] prior to [ * ] but gives no assurances such target will be
            achieved.

      3.    [ * ] LEDs shall have the same physical size as Seller's GaN LED
            Products as described in Attachment A. Except as provided above in
            paragraph (A)(2), [ * ] LEDs will meet or exceed Seller's GaN LED
            Products with respect to reliability.

      4.    Seller supplied engineering samples of [ * ] LEDs in July 1998 and
            will supply qualification samples of [ * ] LEDs in [ * ]. Such
            engineering samples are Confidential Information of Seller.
            Purchaser will use such samples solely for evaluation and will not
            disclose the samples to any third party without Seller's written
            consent.

      5.    Seller acknowledges that Purchaser has a need for improved
            specifications for the [ * ] LEDs to meet market requirements.
            Seller agrees, so long as this Agreement remains in effect, to use
            all commercially reasonable efforts to improve the specifications of
            the [ * ] LEDs to those specifications found necessary to meet such
            market demand. Seller further acknowledges that Purchaser's desired
            target specification to meet such market demand is as follows:

                                     Page 7
<PAGE>

             ------------------------------------------------------------------
                                                 Forward         Dominant
             Description      Brightness         Voltage        Wavelength
                          -----------------------------------
                            Typ.      Min.     Typ.   Max.
             ------------------------------------------------------------------
             Green         [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
             ------------------------------------------------------------------
             ------------------------------------------------------------------
             Blue          [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
             ------------------------------------------------------------------
             ------------------------------------------------------------------
             Signal Green  [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
             ------------------------------------------------------------------
             ------------------------------------------------------------------
             "GM" Blue     [ * ]     [ * ]    [ * ]   [ * ]        [ * ]
             ------------------------------------------------------------------

C.    SiC Wafers.

      Product Specifications for SiC Wafers under this Agreement shall be those
      set forth in Attachment B to this Schedule, which are the specifications
      currently used by Seller for its own internal production of LED Products.

D.    Inspection Procedures.

      1.    Seller will test and inspect all GaN LED and [ * ] LED Products in
            accordance with the quality assurance procedures described in
            Seller's document CPT-026 dated July 17, 1997 and will ship only
            units passing such procedures.

      2.    Seller will test and inspect all SiC Wafer Products in accordance
            with the quality assurance procedures described in Seller's document
            CSP-012 dated March 31, 1998 and will ship only units passing such
            procedures.





                                     Page 8
<PAGE>




                                                                    ATTACHMENT A

Information in attachment omitted in its entirety and filed separately with the
Commission pursuant to a confidential treatment request under Rule 24b-2 of the
Commission.




                                     Page 9
<PAGE>




                                                                    ATTACHMENT B

Information in attachment omitted in its entirety and filed separately with the
Commission pursuant to a confidential treatment request under Rule 24b-2 of the
Commission.




                                    Page 10
