Transmission interference fringes from 2690 to 320 cm−1 for InAs and from 1330 to 320 cm−1 for CdTe have been analyzed with classical dispersion theory to obtain the room-temperature dielectric constants. For InAs the dielectric constant between the band edge and the reststrahl ε∞ and the static dielectric constant ε0 are: ε∞ = 11.8±0.1, ε0 = 14.55±0.3; and for CdTe: ε∞ = 7.05±0.05, ε0 = 10.60±0.15. These values agree favorably with previously reported values. The absorption of InAs has been measured from 2500 cm−1, near the fundamental absorption edge, to 260 cm−1. Eight absorption peaks were observed between 444 and 269 cm−1 which are attributed to multiphonon combinations with the following characteristic phonon frequencies: TO1 = 222 cm−1, TO2 = 214 cm−1, LO = 196 cm−1, and LA = 143 cm−1. The transmission of CdTe has been observed from 10 000 to 220 cm−1. From 10 000 to 450 cm−1 the transmission is essentially constant at ∼60%. Below 400 cm−1 only two previously reported transmission minima were observed.

High-effciency GaP green light-emitting p-n junctions have been reproducibly grown employing an overcompensation technique in a vertical dipping LPE system. In this technique b~th the n-and p-type layers are grown in a single LPE crystal growth run, eliminating potential interface problems at the junction. For junction material grown at an initial temperature of 900~ the EL quantum effciencies of encapsulated mesa diodes ranged from 0.08 to 0.14% and averaged 0.10% at 5 mA (,~5-10 A/cm2). Minority carrier diffusion lengths (L~Lh) and relative cathode-luminescence efficiency (CL) were measured in a scanning electron microscope. At excitation levels equivalent to current densities of ,~1-10 A/cm2 in a p-n junction, both Le and Z,h range from 3 to 5~ with maximum measured values of Lh = 7.2# and Le --5.6/~ for material grown from 900~ At the same excitation level the CL efficiency of the p-layers was typically found to be approximately 2-3 times that of the n-layers. Typical values for Le, Lh, CL, and the EL effciencies were found to be larger by --,50% for material grown from 900~ compared to similarly grown material from 1000~The major assets of the overcompensation technique are the high degree of reproducibility in obtaining high effciencies and that only a single growth process is necessary to form the p~ junction.

The doping dependence of the bulk efficiency for both n- and p-type GaP:N has been investigated experimentally and theoretically. Experimental data are presented for p-type Zn,N-doped, n-type Te,N-doped, and n-type S,N-doped GaP over a majority-carrier range 5×1016−2×1018 cm−3. The efficiency data and photoluminescent decay time data on the same samples are compared to a simple equilibrium model for the recombination kinetics in nitrogen-doped GaP. The model predicts that the efficiency should scale linearly with the minority-carrier lifetime, majority-carrier concentration, and the nitrogen concentration in the doping range considered. The comparison of the theoretical results with the experimental data shows that the bulk efficiency of p-type material agrees quantitatively with the analytical prediction. For Te- and S-doped material, which have widely different and varying minority-carrier lifetimes, the bulk efficiency of n-type material is shown to depend linearly upon the minority-carrier lifetime over the entire doping range considered. However, the normalized efficiency η/τmc is shown to depend upon the net donor concentration as η/τmc∝(ND-NA)0.5−0.6 above ND−NA≈3×1016 cm−3, independent of the donor, rather than linearly as predicted by theory. This deviation from theory remains unexplained. The data and analysis suggest that screening is of little importance over the doping rane considered. The lower limit on the nonradiative Auger lifetime of the bound excitons in p-type material is determined to be τxA≥(100−200)(1017cm−3/p) nsec. The strong variation of the minority-carrier lifetime with doping for n-type material is attributed to nonradiative centers extrinsic to the nitrogen center because of the different dependences observed for S- and Te-doped material and no firm conclusion can be drawn about the strength of nonradiative Auger recombination.

Articles you may be interested inInherent interface defects in thermal (211) Si / SiO 2 : 29 Si hyperfine interaction AIP Conf.Experimental evidence is presented to establish the existence of a Si,O defect impurity system in GaP. This defect is shown to be a strong nonradiative recombination center in n -type material. A photoluminescence band near 1.55 eV at room temperature has been associated with the Si,O defect.[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

The origins of dislocations in GaP grown by liquid phase epitaxy (LPE) and their effects upon green electroluminescence (EL) efficiency have been investigated by chemical etch pitting and scanning electron microscopy. Under normal growth conditions, the dislocation etch pit density (Pn) and configuration in the epitaxial layers are controlled by, and are approximately the same as, that in the liquid encapsulated Czochralski substrate. All dislocations which are revealed by chemical etching in the p LPE layer cause a localized reduction in luminescence. The dislocations are shown to behave as regions of rapid (nonradiative) recombination. Typically, reductions of a factor of -2 in green EL efficiency occur when Pn for the LPE layers is in the -2-5 X 10 5 cm-2 range, corresponding to an average separation of about two to four diffusion lengths in this material. The experimental results are supported by a simple theoretical model for the effects of dislocations on EL efficiency. These considerations explain why dislocations in GaP LPE layers for red light-emitting diodes (LED's), in contrast to green LED's, typically have no significant effect on EL efficiency since diffusion lengths are much shorter in the red LED's. PACS numbers: 78.60.F, 85.6O.J, 61.70.M [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 128.82.252.58 On: Tue