On the Auger Recombination Process in P-Type Lpe HgCdTe
- PDF / 359,778 Bytes
- 7 Pages / 420.48 x 639 pts Page_size
- 79 Downloads / 214 Views
ON THE AUGER RECOMBINATION PROCESS IN P-TYPE LPE HgCdTe J.S. CHEN, J. BAJAJ, W.E. TENNANT, D.S. LO, M. BROWN* AND G. BOSTRUP Rockwell International Science Center, 1049 Camino Dos Rios, Thousand Oaks, CA 91360 * Present Address: Grumman Corporate Research Center, Bethpage, NY ABSTRACT Minority carrier lifetime measurements at 77K were carried out in ptype liquid phase epitaxial (LPE) Hg _xCd Te/CdTe (x = 0.22) using the photoconductive decay technique. Lifetimes of 20 to 7000 ns were obtained in samples with hole concentrations, p , in the range 1014 to 1016 cm 3. The hole concentrations were determineg by analyzing the Hall data using a double-layer model. It was found that the minority carrier lifetime is inversely proportional to p01 . 86 . This result demonstrates that the Auger mechanism may be the dominant recombination process in p-type LPE Hgo.78Cdo.22Te/ CdTe. The temperature dependence of minority carrier lifetime was also measured between 10 and 200K for several samples. INTRODUCTION Even though the minority carrier lifetime and recombination mechanisms in HgCdTe have been extensively investigated experimentally and theoretically, most of the studies were focused on bulk HgCdTe [1-15]. In addition, the conclusions of various reports differ drastically. For example, for ntype bulk HgCdTe with x = 0.22, the measured minority carrier lifetimes have been interpreted by different groups in terms of various recombination processes such as Auger [1,4,5,10,11], Shockly-Read [3,4,5,9,12], radiative [1], and even combination of Auger and radiative [1,5]. The number of published results on the recombination mechanism for p-type bulk HgCdTe is much less than that for n-type. However, different conclusions were also arrived at about the dominant recombination process in p-type bulk HgCdTe [2,5-8,14]. The minority carrier lifetime in LPE-grown HgCdTe on CdTe substrates may be shorter than in bulk materials. In addition to bulk recombination, a nearby recombining surface or interface will reduce the lifetime of carriers within a diffusion length (usually comparable to the layer thickness). Little work has been reported on the study of minority carrier lifetime and recombination in LPE HgCdTe [14,16]. This paper presents a systematic study of the minority carrier lifetime in p-type LPE Hgl_xCdxTe with x = 0.22. The recombination process in these p-type LPE layers was investigated by measuring the minority carrier lifetime as a function of temperature and hole concentration. Hall effect measurements were carried out on all the layers to determine the hole concentrations. For low-hole concentration samples that showed negative Hall coefficients and low mobilities, a two-layer model was used to derive the hole concentration. The three possible bulk recombination mechanisms that limit the minority carrier lifetime in HgCdTe are radiative, Auger and Shockley-Read mechanisms. The details of these recombination processes have been described by many authors [1,2,4-8]. The expressions for the lifetimes limited by these three rec
Data Loading...
