The temperature dependence of morphology of InAs islands on Si grown through Stranski–Krastanow mode is investigated by atomic force microscopy. Formation of islands in the range of 15–50 nm is observed for depositions at various temperatures for the same monolayer coverage. Growth temperatures between 400 and 425 °C are found to yield dense ensembles of islands with uniform dimensional distributions. Found to exhibit long-term stability, these islands undergo morphological transformation when annealed at temperatures above 700 °C. Ostwald ripening occurs in these islands through an enhanced surface diffusion mechanism at high annealing temperatures. The results of annealing experiments indicate surface diffusion being the dominant mechanism responsible for morphological changes in these island structures rather than the heterointerface diffusion.

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In addition to the persistent photoconductivity (PPC) attributed to DX centers in GaAs delta-doped with Si, a weak PPC (WPPC) with a PPC carrier density independent of Si-doping concentration has been generally reported at ambient atmosphere, but the nature of the deep states responsible has not been elucidated. Here, we present the results of a detailed study of the WPPC in δ-GaAs:Si at low-doping densities, NSi≈1–3×1012 cm−2, and ambient pressure. It is concluded that the WPPC does not arise from DX centers but from another deep defect, which is DX-like in the sense that it can be metastably excited. The presence of two distinct DX-like states is apparent from two separate annealing temperatures of the PPC, Ta≈50 K and Tb≈230 K; to the best of our knowledge, the latter is the highest annealing temperature observed in the AlGaAs:Si system.

We discuss the many factors affecting the reliability of GaAs HBTs that we have encountered starting from the early days of AlGaAs-emitter HBTs through the present day use of InGaP-emitter HBTs. We discuss both wearout and infancy failure modes and try to distinguish fundamental (i.e., unavoidable) from nonfundamental failure modes. We have found that infant failures are dominated by substrate dislocation density, which can limit long-term-reliable circuit sizes to under ~1000 transistors.

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