Photoelectrochemical ͑PEC͒ etching of p-type GaN has been realized in room temperature, 0.1 M KOH solutions. PEC etching of GaN was achieved by applying a positive bias to the surface of the p-GaN layer through a deposited titanium mask. The applied bias reduces the field at the semiconductor surface, which induced the dissolution of the GaN. The effect of bias on etch rate and morphology was examined. It was found that insulating the Ti mask from the KOH solution with Si 3 N 4 significantly increases the etch rate. The rms roughness of the etched region decreased as the bias voltage increased. Etch rates as high as 4.4 nm/min were recorded for films etched at 2 V.

Al /u :GaAs /n :Ga 0.52 In 0.48 P inverted-structure (GaAs on top) Schottky diodes on n+ GaAs (001) substrates have been grown by gas source molecular beam epitaxy with several GaAs thicknesses from 10 to 100 nm. The barrier height determined by the capacitance versus voltage method is substantially higher than the barrier height determined by the current versus voltage method. These results suggest that there is a negative interface charge 6–8×1011/cm−2 at the GaAs/Ga0.52In0.48P interface, which is opposite in sign to the interface charge at the normal structure of the Ga0.52In0.48P/GaAs heterojunction reported previously.

The potential of III-nitride materials for the fabrication of bipolar transistors is investigated theoretically. Several different AlGaN/GaN n–p–n heterojunction bipolar transistor structures are examined through calculations of their band profiles and majority carrier distributions in equilibrium and in forward active mode. Spontaneous and piezoelectric polarization charges are utilized to create large hole sheet carrier densities in the base layer, thus minimizing the base spreading resistance. At the same time, a large accelerating field in the base can help reduce the base transit time of the electrons and, hence, increase the current gains of these devices. The temperature dependence of the hole concentration in the base is also investigated.

Uniaxial compressive stress was applied to an AlGaAs/GaAs heterojunction. The uniaxial stress coefficients of sheet resistivity, sheet electron concentration, and mobility were obtained. The hydrostatic pressure coefficient of sheet resistivity was also obtained and was used to explain the different magnitude of the uniaxial stress coefficients of sheet electron concentration in the [110] and [11̄0] directions. We obtain a value for the piezoelectric constant e14 of AlAs to be −0.26 C/m2, compared to the value −0.225 C/m2 calculated by K. Hübner [Phys. Status Solidi B 57, 627 (1973)].

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