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The degradation behavior of the sulfur-treated InP surface at relatively low temperature has been investigated with x-ray photoelectron and photoluminescence (PL) spectroscopy. The results showed that the treated surfaces were oxidized to In2O3, InPO3, and InPO4 at 250 °C and in a vacuum of 10−3 Torr for 20 min. As the holding time for S-treated InP under a vacuum of 10−3 Torr increased, the PL peak caused by the band edge transition decreased without the formation of oxides. It was therefore suggested that the decrease of the PL intensity for S-treated InP is only related to the generation of phosphorous vacancies at the surface, not to oxide formation. The usefulness of a thin S overlayer on III–V semiconductors was also discussed.

The effect of sulfur (S) treatments on InP is investigated by low‐temperature photoluminescence (PL) measurements. For both n‐ and p‐InP, the PL intensity is observed to increase about four times in magnitude if the scattering by the S overlayer is relatively small. Some PL bands are observed to disappear after S treatments and then reappear if the S‐treated surface is heat treated at 220 °C in a vacuum of 10−3 Torr. By observing their dependence on the excitation power density, the doping level of the samples, and measurement temperature, these PL bands are ascribed to the optical transitions via surface states. Our results thus indicate that the S‐treated InP surface may not be stable at a subsequent processing temperature of about 250 °C.

The applicability of the constant‐capacitance method to the characterization of the charge trapping mechanisms in the insulator of a metal‐insulator semiconductor (MIS) is demonstrated. It is simple, time saving, and particularly useful in a III‐V compound semiconductor MIS where the density of fast interface states may be high. Under constant capacitance, the measured diode current is directly related to the average distance that the injected charges travel before being trapped within the insulator. This method was applied to Al/silicon‐nitride/InP MIS capacitors where silicon nitride films were formed by plasma‐enhanced chemical‐vapor deposition (PECVD). From the measurements, it was found that charge trapping by direct tunneling is dominant near the silicon‐nitride/InP interface under a low insulator field, and the injection of electrons to the bulk of the silicon nitride assisted by the electric field occurs at a higher insulator field. It is also confirmed that the trap density near the silicon‐nitri...

Polycrystalline silicon thin-film transistors show a 1/fγ (with γ

The growth of high quality CdTe epitaxial films on p‐InSb(111) by a simple method of temperature gradient vapor transport deposition was carried out to investigate the possibility of the existence of a two‐dimensional electron gas with high mobility at CdTe/InSb heterointerfaces. From the x‐ray diffraction analysis, the grown layer was found to be a CdTe epitaxial film. Photoluminescence measurements at 15 K showed that a CdTe film grown on InSb(111) in the temperature range between 180 and 280 °C appeared to have an optimum crystal perfection at a substrate temperature of about 245 °C. These results also indicated that the CdTe films grown above 245 °C contained a significant problem due to interdiffusion from the InSb substrates during the growth.

A remote plasma‐enhanced oxidation method, with two different reactant gases of N2O and POCl3, is used to grow stable insulating layers on an InP substrate. The compositional profile of the oxide grown with N2O reactant was very similar to that of thermally grown oxide. The hysteresis of capacitance‐voltage (C‐V) characteristics in this system was relatively small and determined by the compensative effects of mobile charges in the oxide and the capture of electrons at the interface. The very unstable nature of the C‐V characteristics in the metal‐insulator‐semiconductor (MIS) diode prepared with POCl3 reactant seems to be related to the gradual nature of the interface and/or the P‐oxide deficiency at the interface. Even if a stable oxide layer of InPO4 can be grown by POCl3 plasma, the very poor nature of the transition region must be overcome to achieve a good MIS structure.

In this article, we present an in-depth study of the effects of the structural and optical properties of InAs “dots in an In0.2Ga0.8As well” (DWELL) and InAs “dots in an asymmetric In0.2Ga0.8As well” (asym. DWELL) grown by migration-enhanced molecular beam epitaxy. The energy spacing (ΔE1) between the ground-state and the first-excited-state transitions increases from 66 meV for the DWELL to 73 meV for the asym. DWELL. These results are consistent with ΔE1 measured by photoluminescence excitation and the values of activation energy fitting. The photoluminescence linewidth of the asym. DWELL (40 meV) is narrower than that of the DWELL (70 meV), which shows superior uniformity in the former over the latter. The trends of the properties of the DWELL and the asym. DWELL deduced from the structural properties are in good agreement with those from the optical properties. From the results, it is strongly supported that the asym. DWELL is more suitable for application to long wavelength optical communication than...

We investigated the surface electronic structure and magnetism of the NiAs structured MnAs(0001) and MnSb(0001) using first-principles full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation. We considered the Mn- and anion(As or Sb)-terminated surfaces for both the MnAs(0001) and MnSb(0001) systems. The calculated magnetic moments of the surface Mn atoms for Mn-terminated MnAs(0001) and MnSb(0001) systems are much enhanced to have 3.79μB and 4.04μB, respectively, compared to the corresponding center layer values, 3.10μB and 3.32μB. The anion atoms in the Mn- and anion-terminated systems have negative magnetic moments with the values between −0.09μB and −0.18μB. The effects of surface termination and the band hybridization on the magnetism and the electronic structure are discussed with the calculated density of states.

We have investigated the half-metallicity and magnetism at the surface and interface of CrS(001) on GaAs using the full-potential linearized augmented plane-wave method within the generalized gradient approximation. Two different terminations, Cr-terminated and S-terminated surfaces, have been considered. We found, from the calculated local density of states, that both of the Cr-terminated and the S-terminated surfaces retain the half-metallicity, but the band gap for the S surface is much reduced compared to that of bulk. The magnetic moment of the Cr-terminated surface (4.08μB) is enhanced much compared to the value of bulk (3.61μB) while that of the interface Cr (3.29μB) is smaller than the bulk value.

We have studied the relaxation or decay of the perpendicular remanent magnetization of CoCr films after the removal of a saturating magnetic field. The films have a perpendicular anisotropy and are similar to those being studied for application as perpendicular recording media. The time dependence of the decay of the magnetization was determined by measuring the magnitude of the magnetization continuously for time periods up to a thousand minutes using a SQUID magnetometer. This time dependence was studied over a range of temperatures for each of the samples (10–300 K). The decays are found to be quasilogarithmic over at least three decades of time and have been compared to two phenomological models. A fit to one model’s decay rate indicates the temperature dependence of the decay rate is nonmonotonic, i.e., the decay rate is a maximum in an intermediate temperature region for the films we have studied.

A low‐noise medium that shows potential for future high‐density longitudinal magnetic recording applications has been prepared and studied. The disk consists of a CoCr‐based ternary alloy and a few percent of a third transition metal sputter deposited on a Cr underlayer. The media noise power is low and nearly frequency independent up to 80 kfci, in sharp contrast to the noise power spectra typical of metal films. Because of the exceptionally low media noise, we have obtained signal‐to‐noise ratios (SNR) greater than 35 dB up to 30 kfci on media having a 70% amplitude density (D70) of 20 kfci. Other characteristics of the media include overwrite better than −35 dB, saturation magnetization of 500 emu/cm3, and coercivity of 1300 Oe. The grain diameter, coercivity, and D70 depend strongly upon the Cr underlayer thickness. The data suggest that the low‐noise results from reduced intergranular exchange coupling.