Orientation-dependent etching of silicon by aqueous KOH is a standard procedure in the microelectronics industry. We have measured the etching products by recording the Raman spectra in real time as the etching of{100} silicon progressed in a 5M KOH solution. The primary etching species has been determined to be OH , and the etching products have been determined to be the silicate SiO2(OH)L Isopropyl alcohol does not appear to participate chemically in the etching process.Aqueous KOH is used as an orientation-dependent etching solution (1) throughout the microelectronics indUstry to make a variety of silicon devices such as V-grooves for VlVIOS transistors (2, 3), pyramids for field-emitter arrays (4), small holes for ink jets (5), and thin-wall Josephson junctions (6). Previously re-
The indirect band gap of icosahedral B 12 As 2 (IBA) has been determined by variable temperature photoluminescence measurements (8 K-294 K) on solution-grown bulk samples. In addition, evidence of three shallow acceptor levels and one shallow donor level is reported. The lowtemperature spectra were characterized by broad and intense deep defect emission, donor-acceptor pair (DAP) bands, and exciton recombination. The appearance of DAP emission verifies the incorporation of a donor in IBA, which has not been reported previously. The temperature dependence of the free exciton (FE) intensity reflected a FE binding energy of 45 meV. The variation of the FE peak position with temperature was fitted with both Varshni and Pässler models to determine an expression for the temperature dependence of the indirect band gap. The resulting low and room temperature band gaps are E g (0) ¼ 3.470 eV and E g (294 K) ¼ 3.373 eV, respectively. The latter is not consistent with previous reports of the room temperature band gap, 3.20 eV and 3.47 eV, derived from band structure calculations and optical absorption, respectively. The origin of these discrepancies is discussed. The DAP spectra reveal three relatively shallow acceptors with binding energies of %175, 255, and 291 meV, and a shallow donor with binding energy %25 meV. Although the identity of the individual acceptors is not known, they appear to be associated with the light-hole band. The small donor binding energy is suggestive of an interstitial donor impurity, which is suspected to be Ni. V C 2012 American Institute of Physics.
The conversion of semi-insulating GaAs to p type as a result of heat treatment in H2 was studied by photoluminescence (PL), secondary-ion mass spectrometry (SIMS), and transport measurements. The SIMS measurements resulted in the direct chemical identification of Mn near the heated surface. The correlation of the SIMS profiles with the results of PL and transport measurements indicated that Mn acceptors are responsible for the type conversion, and that substantial concentrations of Mn(?1017/cm3) are found in thin (1–3 μm) layers near the surface. The results of studies of samples heated under several different conditions showed that the Mn layers were not introduced by contamination from external sources during heat treatment, but were probably due to the presence of a bulk Mn concentration (<3×1015/cm3): during heat treatment the Mn diffuses to the surface, probably assisted by the in diffusion of Ga vacancies, as suggested by Zucca. Photoluminescence profiling measurements and the correlation between the SIMS and PL results indicate that the 1.41-eV PL band that is associated with the type-converted surface is due to recombination at a Mn acceptor on a Ga site, and not at a next-nearest-neighbor arsenic vacancy-amphoteric acceptor complex.
A new photoluminescence band at 1.3975 eV has been observed in a bulk crystal of Sb-doped InP. On the basis of its photon energy, line shape, radiative decay time, and correlation with the presence of Sb, it is suggested that the new luminescence band is attributable to the radiative recombination of excitons bound to Sb imp irities which substitute isoelectronically on the P sites.
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