CBE growth of InP using BPE and TBP: a comparative study

Abstract

Results of a comparative study on the growth of indium phosphide (InP) by chemical beam epitaxy (CBE) using two alternative phosphorous (P)-precursors, bisphosphinoethane (BPE) and tertiarybutylphosphine (TBP), are presented. For both P-precursors, ethyldimethylindium (EDMIn) was used as the indium (In) precursor. TBP has gained wide acceptance in gas phase growth techniques such as organometallic vapor phase epitaxy (OMVPE) and CBE and its variants. However, BPE has not been extensively applied to CBE growth with only preliminary results of CBE-grown InP using BPE having been published to date. This paper presents the first systematic study on the growth rate and efficiency, morphology, electrical and optical properties of CBE-grown InP using BPE. We compare these results to data obtained for CBE-grown InP using TBP. To make this comparison more meaningful, all TBP and BPE growth runs were performed in sequence using the same CBE hardware under identical experimental conditions. Duplicate sets of sample runs were grown to verify reproducibility. Details of the effects of substrate temperature, cracker cell temperature and V III ratio on the electrical transport properties determined from 77 K and room-temperature Hall measurements and the optical properties characterized by 14 K photoluminescence (PL) measurements are presented. The Hall carrier concentrations and PL data strongly correlate with the sulfur impurity levels measured by secondary ion mass spectroscopy (SIMS). All of the undoped InP epitaxial layers show n-type conductivity. Striking similarities in the electrical and optical properties of InP grown using either BPE or TBP were observed indicating that BPE and TBP, in many respects, can be viewed as interchangeable P-sources.