No abstract

We describe our approach to fabricating X-band power FETs by direct implantation into MBE-grown GaAslSi incorporating low-temperature buffer layers. The devices fabricated on GaAs-on-Si wafers were compared directly to GaAs ion-implanted FET wafers that were processed together in the same lot. We adapted the MBE low-temperature buffer layer for the first time to GaAs-on-Si to provide a high-resistivity layer to prevent Si out-diffusion from the Si substrate and to reduce strain in the GaAs layer. Excellent dc and RF device performance was obtained from both the GaAs/Si wafers and the GaAsl GaAs wafers. The wafers were put through our standard 0.5 bm power FET production process. The sheet resistivity, the transconductance, the Idss channel current, and the pinch-off voltages of the GaAs/Si devices were very comparable to those of the GaAslGaAs wafers. We completed on-wafer dc and RF testing and mapping to correlate material characteristics with device RF performance. The functional RF yield from on-wafer RF probing tests was very high for both GaAs/Si and GaAs/GaAs wafers, varying between 68 and 90 percent for GaAs/Si wafers and 94 and 97 percent for GaAsiGaAs wafers. Although the dc characteristics of the GaAs/Si wafers were very comparable to the GaAs wafers, the RF characteristics were slightly worse, showing 2 dB less maximum available gain than the GaAslGaAs wafers.