Photoetching using a
CrO3‐HF‐AgNO3
aqueous solution was studied in an attempt to reveal inhomogeneities of n‐type
normalGaAs
. This method enabled us to obtain etch patterns of striations and dislocations with high resolution. In addition, an etch depth for revealing dislocations was only about 0.1 μm and striations were delineated with an etch depth of about 0.6 μm. The method was applied to the examination of defects in‐depth, and it was possible to identify independent dislocations and dislocation networks. The activation energy for etching in the dark was 7.5 kcal/mol, which is for the diffusion controlled process. The etch rate increased linearly with illumination intensity and the increases of etch rate under illumination were almost independent of etch temperatures and the concentrations of Ag+ ions. Photoetched patterns were ridged at defects, in contrast to recessed patterns revealed in the dark. This result suggests that the distribution of charges on the surface, including minority carriers (holes) and/or light‐induced electron‐hole pairs, plays an important role in revealing defects.
A flying-spot scanner that employs a chopped photon beam emitted from a cathode ray tube is reported. The photon beam scanns a planar p-n junction put on a metal electrode through a In2O3-coated transparent electrode and a 15 µm-thick mylar spacer. The ac photovoltage is picked up with electrodes through a condensor formed by the spacer. The photovoltage signal modulates brightness of another cathode ray tube to form a scanning image. Mean wavelength and chopping frequency of the photon beam are 507 nm and 2 kHz. Scanning image analysis is done using photocurrent density equations based on a step-like junction model. Three kinds of junctions, a solar cell, a partly-deep junction and a non-uniformly ion implanted one, have been evaluated to show the validity of the present method.
Pinholeless polycrystalline indium phosphide layers were grown on molybdenum sheets at temperatures lower than 600°C using indium and phosphorus trichloride as the source materials. The low activation energy of the deposition rates and weak dependence of the rates on the partial pressure of indium monochloride suggest that surface processes play an important role in the growth of polycrystalline films. It was ascertained by an x‐ray diffraction measurement that the {110} and {331} orientations become noticeable with increasing thickness at higher temperatures, whereas the <111> orientation is dominant at lower growth temperatures. The development of the <110> orientation produces films with a columnar structure, which could be explained by the dependence of the growth rate on the crystallographic orientation.
Flying-spot scanning images of a chemically etched p-type polycrystalline Si wafer, 60 mm in diameter, are obtained nondestructively using the AC photovoltage excited by a visible photon beam chopped at 2 kHz. The AC photovoltage is concluded to be the surface photovoltage correlated with the native oxide layer. After thermal annealing in N2 ambience at 850 degrees C for 60 min, the surface image drastically changes. This might be due mainly to fixed oxide charge modification and partly to variation in the minority carrier diffusion lengths.
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