Te-rich Conditions Research Articles

Electrical activity, mode of incorporation and distribution coefficient of group V elements in Hg1−xCdxTe grown from tellurium rich liquid phase epitxial growth solutions

Hg1−xCdxTe films were grown liquid phase epitaxially from tellurium rich solutions containing up to 10 at. % of the group V elements P, As, Sb, and Bi. Chemical analysis of the Te growth solutions and the films was carried out in conjunction with extensive Hall effect measurements on the films subsequent to various annealing treatments under Hg rich and Te rich conditions. Despite the presence of a large concentration of the group V elements in the Te source solution, the maximum concentration of these elements incorporated into the liquid phase epitaxially grown Hg1-xCdxTe appears to vary from <1015cm−3 for Bi up to 1017cm−3 for phosphorus and As implying a distribution coefficient varying from <10−5 for Bi up to 10−3 for P at growth temperature of ∼500° C. This low value of the distribution coefficient for group V elements for growths from Te rich solutions contrasts with the moderately high values reported in the literature to date for growth from Hg rich solutions as well as pseudobinary solutions (Bridgman growth). The widely differing distribution coefficients and hence the solubility of the group V elements for Hg rich and Te rich liquid phase epitaxial solutions is explained on the basis that the activity coefficient of the group V elements in Te rich solutions is probably orders of magnitude lower than it is in Hg rich solutions. Finally, the results of the anneals at 200° C under Hg saturated conditions with and without a 500° C Hg saturated preanneal have indicatedn top conversion in many of the films attesting to the amphoteric behavior of the group V elements in LPE grown Hg1−xCdxTe(s) similar to the previously reported behavior of P in bulk grown Hg0.8Cd0.2Te.

A Study of the MBE HgTe Growth Process

ABSTRACTThe MBE growth of HgTe on CdTe is examined over a hundred-fold range in Hg/Te2 flux ratio and over four separate substrate surface orientations [(111)Te, (111)Te-4 degrees, (112)Te and (001)]. The 77K Hall mobility of the (112)Te and (001) oriented HgTe layers approaches the best bulk values reported to date, although our (111)Te and (111)Te-4 deg oriented HgTe films yield much lower values. The growth process is shown to be very far from thermodynamic equilibrium at our optimal substrate temperature and calculated equivalent Hg beam pressure. Important clues to help understand the kinetics governing the HgTe growth process are uncovered by studying the defects that form under Hg- or Te-rich conditions with cross-sectional transmission electron microscopy (XTEM). Since multilayered structures are an important application for MBE growth of Hg-based semiconductors, we have also examined the interfacial roughness present in HgTe-CdTe superlattices (SL) as a function of growth orientation.

The solubility and diffusivity of In in CdTe

The solubility and diffusivity of In in CdTe has been investigated in the temperature range 200-850 degrees C, under Cd-rich and Te-rich conditions, using a radiotracer method. The diffusivity is independent of In concentration and below 400 degrees C is also largely independent of temperature. Above 400 degrees C the solubility and diffusivity depend on both temperature and non-stoichiometry. At Te saturation D(In)=6.48*10-4exp(-1.15 eV/kT) cm2s-1and at Cd saturation D(In)=117 exp(-2.21 eV/kT) cm2s-1. The results are discussed in terms of the defect chemistry of CdTe.