Wafer-level correlations of EL2, dislocation density,and FET saturation current at various processing stages

The neutral deep-donor density [EL2]⁰, and dislocation density,ρ _D, are measured on adjacent, semi-insulating GaAs wafers, grown by both high-pressure (HP) and low-pres-sure (LP) liquid-encapsulated Czochralski (LEC) techniques; also, other nearby wafers from each boule are used for low-noise, field-effect-transistor (FET) fabrication. Dense data maps (at least 3500 points per wafer per parameter) are then visually and math-ematically compared for [EL2]⁰,ρ _D,I _u, I_r, and I_g where the latter three quantities rep-resent the unrecessed-ungated, recessed-ungated, and gated saturation currents, re-spectively, for ion-implanted, 0.5 ]smm × 300 μm FET’s. For theparticular wafers and processing used in this study, the following conclusions can be drawn: (1) onall of the wafers, materials (EL2 andρ _D) non-uniformities are correlated with at least some of theI _u non-uniformities; (2) onsome of the wafers, materials non-uniformities follow all the way through toI _g, but on others, the gate-recess step itself introduces much stronger non-uniformities; (3) the HP-LEC wafers give slightly higherI _u’s than the LP-LEC waf-ers; and (4) [EL2]0 is a better predictor ofI _u than isρ _D.     

Impact of wide bandgap microwave devices on DoD systems

Radiofrequency (RF) semiconductor electronics enable military systems that operate in the microwave and millimeter wave frequency bands of 1-100 GHz. The performance of numerous electromagnetic systems could be enhanced by the inclusion of wide bandgap (WBG) microwave and millimeter wave devices, either as power amplifier or receiver elements. The demonstrated power performance has generally been six to ten times that of equivalent gallium arsenide or indium phosphide devices up through 20 GHz, with enhanced dynamic range and improved impedance matching. These characteristics provide an opportunity to significantly reduce the number of modules required for many active aperture antenna systems, hence, cost, while enabling new capabilities for shared apertures. Prior to realization of any WBG system deployment, however considerable development and maturation of WBG materials, devices, and circuits must yet ensue.