New results for nonstoichiometric InP grown by low temperature MBE

We report the first observation of lattice contraction in nonstoichiometric InP grown by low temperature MBE. The lattice contraction is caused by P antisite defects, that is the smaller P atom occupying a group III lattice site that the larger In atom would normally occupy. We have studied the MBE growth of InP over a temperature range from 150-350C. We show that there is a narrow range of growth temperatures where crystalline InP can be grown with a measurable amount of excess P. The InP layers grown below this temperature range will incorporate very large amounts of excess P and become amorphous, while InP layers grown above this temperature range will not have measurable amounts of excess P. The as-grown InP is very conducting because the P antisite behaves as a shallow donor. Our TEM images of annealed crystalline nonstoichiometric InP show that P precipitates are formed. As the P precipitates are formed, the conductivity decreases. The crystalline nonstoichiometric InP behaves analogously to low temperature grown GaAs. However, for the amorphous InP samples grown at lower growth temperatures the conductivity increases with anneal. The different growth regimes that we describe in this paper may help to explain the varied results obtained in previous reports on LT InP.