Admittance spectroscopy on buried GaSb junctions due to defect distribution in GaAs/GaSb metalorganic vapor phase epitaxy heterostructures

摘要

Admittance spectroscopy was employed to investigate the electrical properties of buried GaSb homojunctions. A strong p-type surface layer was obtained in n-type GaSb bulk crystals through diffusion of Zn atoms. The acceptor impurities were introduced into Te-doped substrates by epitaxially growing a heavily p(Zn)-doped GaAs layer. Current-voltage investigation, after the removal of the GaAs cap layer, demonstrated the formation of the GaSb p-n homojunction. However, the p-n interface of the junctions resulted to be not due to the presence of Zn. In fact, secondary ion mass spectrometry pointed out only a small penetration depth of Zn atoms in the GaSb substrate (～100nm), whereas electron beam induced current investigation demonstrated that the p-n junction interface was located more deeply into the substrate (～1 μm). Admittance spectroscopy and capacitance-voltage investigations led to attribute the change of conduction type from n to p of GaSb beyond the Zn penetration depth to the formation of lattice acceptor defects, influenced by the thermal annealing processes during and after the GaAs growth. An attempt to explain the formation of the buried junction in terms of atomic inter-diffusion is provided, in order to justify, from a microscopic point of view, the low diffusivity of Zn in GaSb, and the depth of the p-n junction interface in the substrate.