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A new type of transistor called the miniband base transistor is proposed and fabricated. The miniband base transistor uses, as an entire base layer, a superlattice of the same conduction type as an emitter and a collector. The superlattice base is designed so that the injected electrons are in the first excited miniband, while base current carriers are in the ground miniband. The minigap between these two minibands is expected to suppress LO-phonon scatterings and to increase the current gain. The transistor is fabricated using an AlGaAs/GaAs superlattice. Electrical measurements indicate that the superlattice base is effective for improving the current gain of the hot-electron transistor at small collector voltage.

Reflection high‐energy electron diffraction (RHEED) intensity oscillation during sublimation of GaAs is observed at high substrate temperatures above 690 °C. This post‐growth RHEED intensity oscillation suggests that the sublimation occurs layer by layer. One period of this oscillation precisely corresponds to sublimation of one monolayer. Aluminum arsenide acts as a sublimation stopper. The sublimation rate was measured accurately as a function of substrate temperature.

Reflection high‐energy electron diffraction (RHEED) intensity oscillations during Si molecular beam epitaxy (MBE) are observed for the first time. It is revealed that stable RHEED intensity oscillation exists during the MBE growth of a single‐element semiconductor. The stable oscillations were observed only after preheating treatments. The substrate temperatures for the oscillation were from as low as room temperature to 1000 °C. One period of the oscillation corresponds to atomic‐layer or biatomic‐layer growth on the concerned surface. Oscillation of more than 2200 periods (∼6000 A) was observed. One oscillation period can be as slow as 38 min.

Long lasting RHEED oscillations during MBE growth of GaAs and Al x Ga1-x As are observed. Using these oscillations, accurate measurements of GaAs, Al x Ga1-x As growth rates and the Al mole fraction x were performed during the growths. The phase of the RHEED oscillations was analyzed by computer and molecular beam shutters were operated at a particular phase. This computer controlled phase-locked epitaxy (PLE) was applied to grow precisely defined (GaAs)2(AlAs)2 bi-layer superlattices. Raman scattering spectra showed split lines characteristic of superlattices. This PLE method is invulnerable to molecular beam fluctuations.

The effect of an undoped spacer layer up to 300 A thick adjoining a triple-barrier diode is studied. Larger peak-to-valley ratios and smaller full-widths at half maximum (FWHM), compared to conventional triple-barrier diodes, are obtained for the resonant current-peaks in these samples. It is explained that a main cause of the peak broadening is the random distribution of silicon ions in the heavily doped layer adjoining the barrier.