Growth of Semi-Insulating Cadmium Telluride

Abstract

A modified Bridgman method for growing cadmium telluride is described. This method controls the composition of the melt, and thus the solid, by controlling the pressure of one of the components of cadmium telluride (CdTe) over the melt. The theory of equilibrium between solid-liquid-gas for this system indicates that the liquid acts only as a transferring medium between gas and solid. Thus the system may be treated as a gas-solid system with respect to defect chemistry. The synthesis and purification of CdTe is described in detail, and empirical results for producing large single crystals are given. Crystals grown by this system are compared with the defect chemistry presented by de Nobel. D. de Nobel (1) has shown that cadmium telluride (CdTe) can undergo stoichiometric deviations, and that such changes in composition are caused mainly by lattice defects which determine the conductivity Key words: crystal growth, cadmium telluride, semi-insulating cadmium telluride, II-VI compound, radiation detector material, modified Bridgman crystal growth, optical modulator material. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2015-02-08 to IP Vol. 118, No. 11 GROWTH OF SEMI-INSULATING CdTe 1791 I_ m L. A9 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2015-02-08 to IP * Electrochemical Society Active Member.cedures distinction can be made between the properties of weak spots in the insulator and those of the bulk (1). We have observed electrical switching in zirconia films, grown by thermal and anodic means on zirconium and a number of its alloys. Areas of impurity and intermetallic precipitates have been identified as ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2015-02-08 to IP

Evidence for In-defect complexes in CdTe

“…A CdTe single crystal was grown following a modified Brigdman method under excess Cd vapour (Kyle 1971). Slices of 1.3 mm thickness were prepared from the rod.…”

Effect of Excess Component Element during LPE on Electrical Properties of CdTe

“…Phosphorus is considered to be a shallow acceptor substituting Te site. As the reaction of defect formation and ionization, the aforementioned formulas [1]- [3], [6]- [9], and the following are considered PXTe ~-P~we "~-e' K7 : 0.hpo exp (--AET/kT) [15] Charge neutrality equation The value of K7 is listed in Table I. The equilibrium reactions of phosphorus itself with vapor phase are neglected.…”

“…It has been established that the performance of many compound semiconductor devices is adversely affected by nonradiative recombination centers. Their presence in'the device active region leads to a decrease in the device efficiency [as in the case of solar cells (1) ]. Furthermore, the recombination-enhanced diffusion of such centers (2) causes a slow degradation of the device performance [as in the case of semiconductor lasers (3) ].…”

“…It is desirable that the crystal growth is carried out under a well-defined pressure of component element in order to control the material properties. It has been reported as for CdTe that the electrical properties of bulk crystals grown under different Cd vapor pressures are very different (1,2).…”

Minority Carrier Diffusion Length EBIC Measurements in Cadmium Telluride

“…Comparison of the results for specimens 20 and 3 suggest that growth by the modified Bridgman method (8), involving a Te molten zone and a temperature of about 750~ does not automatically result in a longer hole diffusion length than the normal Bridgman method at ll00~ However, the sample comparison is limited and one cannot help feeling that the lower temperature process should allow less contamination from the system (8,16). Ge and Sn are considered to have adverse effects on lifetimes on CdTe but little is reported about the effects of Si.…”