Photocapacitance study of pressure-induced deep donors in GaAs: Si

Abstract

concluded that these pressure induced deep donors (to be abbreviated as PIDD in this article) in GaAs are identical to the DX centers in GaAlAs.To substantiate this conclusion it is necessary to compare all the known properties of the DX centers with that of the PIDD in GaAs.The hydraulic press at room temperature. The pressure was determined by the standard ruhy fluorescence technique. 5Two optical measurements have been performed to study the properties of the PIDD in GaAs. In the first experiment the dependence of the electron photoionization cross section (a~) of deep centers on incident photon energy was measured. In the second experiment the thermal capture rates of optically excited carriers were determined at low temperatures. From these capture rates the decay times of free carriers in PPC can be calculated.In the first experiment light from a tungsten halogen lamp is focussed into a monochromator with a spectral width of 7 nm. The radiation from the monochromator is directed into the diamond anvil cell and scattered by the powder surrounding the sample. Since the diode is covered by metal electrodes on both the too and the bottom, only the 3 scattered light can enter the sample from the sides. As a result it is not possible to determine exactly the amount of light absorbed by the sample, however, it is still possible to measure the relative an() provided we assume that the light scattering efficiency is constant over the range of photon energies in this study. Except for this assumption we have corrected for the dispersion in the diamond absorption and in the lamp emission. As a test of the reliability of our measurement we have used the same setup to measure the dispersion of the u; of GaAlAs:Te at atmospheric pressure and compared our results with those reported by Lang et a1. 3We have used the method of Chantre et a1. 6 to measure CT~. The sample, whether GaAlAs at atmospheric pressure or GaAs under pressure, was first maintained at zero bias at room temperature in order to fill the traps and then cooled to 77 K in the dark. A reverse bias of 3 V was then applied to the diode. As the thermal emission rates of the DX center and the PIDD in GaAs at 77 K were both negligible, the traps in the depletion layer remained occupied. Next the sample was illuminated with radiation from the monochromator and the rate of change in the diode capacitance was measured. Since the change in capacitance was proportional to the change in the electron concentration in the deep centers (n 1 ) within the depletion layer we obtained in this way dnr/dt.If ~is the incident photon flux density, cT; and G"; are respectively the electron and hole photoionization cross sections for the deep center, then it has been shown that dnT/dt is given by:6 dn 1 /dt =£(hv) [a-;(hV)where NT is the concentration of deep centers and hV is the photon We note that the corresponding value for the DX center in GaAlAs:Si obtained by Lang and Logan was 1.25 eV 11 • On the other hand we could not obtain any reasonable fit to our results by assuming...

Persistent photoconductivity and optically stimulated luminescence in Zn 0.8 Mg 0.2 Se mixed crystals

“…The decay of the photocurrent according the power law has been observed in many inhomogeneous binary and ternary semiconductors and in modulation doped amorphous silicon [1,3,13,21,22]. It has also been shown that in some ternary II-VI and III-V solid solutions at low temperatures the relaxation of PPC shows a stretched-exponential behavior but the link between those two types of decay has not been established yet [8].…”

Dielectric resonator-based resonant structure for sensitive ESR measurements at high-hydrostatic pressures

“…With only minor modifications, this technique has also been used for various dc-and ac-impedance studies [30,31]. Experiments in the DACs have been carried out over an ultrawide range of hydrostatic pressures reaching $500 GPa [32,33]. Sapphire-anvil cell (SAC), a parent and considerably cheaper modality of DAC, has been used at lower pressures (up to $10 GPa) [34].…”

New electron and hole traps in GaAsP alloy

“…The large capture barrier of trap A is similar to the DX centre (Lang 1986, Mooney 1990, Malloy and Khachaturyan 1993, Li and Yu 1993. It is already clear that DX centre is introduced by a simple substitutional donor (Mizuta et al 1985, Li et al 1987, Chadi and Chang, 1988, 1989, Mooney 1990, Malloy and Khachaturyan 1993, Li and Yu 1993, not a complex of donor impurity and other unknown defect, as suggested by Lang (1986) in early days. The trap A concentration is two orders of magnitude lower than the Te doping concentration.…”