Ga and In Autodoping of Cdt, MnxTe Epitaxial Layers Grown on GaAs and InSb Substrates

Abstract

A study of Ga and In outdiffusion into Cd1−xMnxTe (0≥ x ≥ .70) epitaxial layers grown on (111)GaAs and (001)lnSb was carried out. The layers were grown by pulsed laser evaporation and epitaxy on substrates held at temperatures below 310 °C. The structural quality of the layers was examined using x-ray diffraction and transmission electron microscopy. A tendency toward precipitation of Ga at the near surface region of (11 1)CdMnTe grown on (11 1)GaAs, usually less than 300 nm wide, has been observed with secondary ion mass spectroscopy. Similar results were observed for the migration behaviour of In in (001)CdTe grown on (001)InSb. The ion imaging revealed that both In and Ga accumulate near the surface at localized spots, up to about 10 pm in diameter. The concentration of the spots is in the range of 104 - 106 cm−2. The Ga- and In-rich channels sometimes extend over the whole sample. Annealing at temperatures as low as 400 °C for 2 h significantly increases the concentration of the Ga spots and the average concentration of Ga in the films to above 1016 cm−3. Low-temperature photoluminescence data obtained for annealed samples do not indicate any structural deterioration typical for heavily doped Bridgman grown samples. A sharp neutral-donor bound-exciton transition (D°,X) is observed for samples with 0 < x < .10.

Electrical characterization of CdTe–InSb heterojunctions

“…This is in agreement with the results of PLEE grown samples. (9). Improvement of the interface quality by the use of an overpressure of Cd has been reported during the growth of CdTe on InSb (15).…”

“…Growth of CdTe-InSb heterostructures has been reported using several different techniques including alloying ( 3 , vacuum evaporation (6) molecular beam epitaxy (MBE) (7), organo 'NRC No. 32 696. metallic vapour phase epitaxy (8), and pulsed laser evaporation and epitaxy (PLEE) (9). A number of difficulties in the growth of abrupt, high-quality heterostructures have been identified so far.…”

“…A number of difficulties in the growth of abrupt, high-quality heterostructures have been identified so far. These problems include substrate strain due to solder mounting (lo), fo-rmation of interfacial layers rich in In and Te (1 I), and diffusig and incorporation of In through the CdTe layers (9). The incorporation of other impurities is also of concern, but is more related to the growth environment.…”