Domingo A. Figueredo

GaAs semiconductor‐insulator‐semiconductor field‐effect transistor with a planar‐doped barrier gate

A new GaAs field‐effect transistor structure is proposed and demonstrated. The gate electrode consists of an asymmetric planar‐doped barrier (PDB) diode which behaves like a metal‐semiconductor Schottky contact. The device allows engineering of the gate energy barrier, and optimization of transconductance and gate capacitance for a given application. The larger gate energy barrier in conjunction with the self‐aligned nature of the process holds promise for both large signal analog and digital switching applications.

Contact metallization for producing stable bipolar microwave transistors

Bipolar microwave transistors with Ti/Pt/Au contact metallization show a reversible degradation in current gain (hFE) due to high temperature storage (HTS) stress at 240 °C. This is an elusive effect that occurs only in certain very small cavity, strip‐line packages and only on devices with very shallow emitter‐base junctions (∼1200 A). A model for current gain in shallow‐junction bipolar transistors is described. The model shows that hFE of such devices is very dependent on the properties of the metal–silicon interface at the emitter. The cause of the reversible hFE degradation was found to be hydrogen absorption and desorption in the Ti contact metallization. This causes shifts in the Schottky barrier of the Ti/Si contact with consequent changes in the surface recombination velocity at the emitter. A new contact metallization of W:10 wt. % Ti/Au was developed which is hFE drift free.

Schottky-barrier lowering on gallium arsenide by submicron ohmic contacts

Abstract Although low-barrier Schottky diodes have been fabricated on n-types GaAs using an alloy process, there has been no good model which describes the Schottky-barrier lowering during the sintering cycle. We propose that the lowering of the barrier is due not only to a thin highly-doped region near the Schottky/semiconductor interface, but also to an array of heavily-doped areas separated by higher-barrier regions whose formation depends on the thickness and type of Schottky metals used. It will be shown that such a structure is capable of giving very low forward turn-on voltage, depending on the size of the ohmic areas, while maintaining an acceptable reverse-leakage current.