A predominant deep level with an activation energy of 0.23 to 0.26eV was detected during admittance spectroscopic studies of SnTe-doped layers that had been grown directly onto GaAs substrates by means of molecular beam epitaxy. It was found that the activation energy and capture cross-section of the deep level were similar to the levels that had been detected in S-doped and Te-doped GaSb which had been grown via molecular beam epitaxy. This indicated that the deep level originated from either a native defect or from a common impurity in n-type GaSb. The Sb4/Ga flux ratio was found to affect the Hall mobility and concentration of the deep level in a similar way; with an optimum beam equivalent pressure ratio of about 7 for GaSb which had been grown at 550C. This was suggested to correspond to the lowest ratio that would maintain a Sb-stabilized surface reconstruction. Analysis of the results suggested that the present deep level was a complex defect.

J.F.Chen, N.C.Chen, H.S.Liu: Applied Physics Letters, 1996, 69[13], 1891-3