Abstract: Generally, and in one form of the invention, a method is disclosed for forming an ohmic contact on a GaAs surface 20 comprising the steps of depositing a layer of InGaAs 22 over the GaAs surface 20, and depositing a layer of TiW 24 on the layer of InGaAs 22, whereby a reliable and stable electrical contact is established to the GaAs surface 20 and whereby Ti does not generally react with the In.

Abstract: A bipolar transistor includes a passivating layer of material 40 in the base structure 42 that serves to cover the extrinsic base region of the transistor. The passivating layer 40 is formed of a material having a wider bandgap than the base layer 44, and is heavily doped with the same doping type (n or p) as the base layer. The invention is advantageous in that the base contacts 48 of the device are made directly to the passivating layer 40 and are not in direct contact with the base layer 44. This eliminates the need for alloyed contacts and the concomitant reliability problems associated with spiking contacts. In addition, the invention is completely compatible with self-aligned production techniques.