Selectively regrown ohmic contacts for high frequency and low noise FETs

We investigate highly doped selectively regrown GaInAs ohmic contacts to GaInAs channel FETs to obtain a stable, reliable, and low resistance contact technology. We selectively regrow n/sup +/ GaInAs on various doped-channel FET structures and standard and doped-channel HEMTs. For lower doping concentrations on the regrown GaInAs (n/spl ap/1.5/spl middot/10/sup 18/ cm/sup -3/), we encounter instabilities at higher temperatures in the contacts when HF is employed in the processing steps. However, we achieve temperature stable contacts with a contact resistance of 0.1 /spl Omega//spl middot/mm regardless of the sample's exposure to HF when higher doping (n/spl ap/7/spl middot/10/sup 18/ cm/sup -3/) is incorporated in the regrowth process. We believe that we will be able to use this stable and low resistance contact technology to achieve high performance microwave transistors.