OMVPE GROWTH OF METASTABLE GAASSB AND GAINASSB ALLOYS USING TBAS AND TBDMSB

Epitaxial layers of the metastable alloys GaAsSb and GaInAsSb have bee n grown by organometallic vapor phase epitaxy (OMVPE) using tertiarybu tylarsine (TBAs) and tertiarybutyldimethylantimony (TBDMSb) with conve ntional group III sources. Layers with compositions well inside the mi scibility gap were successfully obtained. The key parameters for obtai ning these metastable alloys are the use of low V/III ratios (less tha n or equal to 1) and low growth temperatures. The Sb distribution coef ficients for GaAsSb are close to unity on both GaSb and InAs substrate s when V/III ratios of approximately unity are used. The distribution coefficients of Sb for GaInAsSb on GaSb and InAs substrates are slight ly higher than unity for lower V/III ratios. The quality of the surfac e morphology is degraded as the composition moves further into the reg ion of solid immiscibility. The hole concentrations of undoped GaInAsS b layers on GaAs substrates grown using conditions identical to those used for the InAs substrates are approximately 1 x 10(17) cm(-3) at ro om temperature. The concentrations of In and Sb in the GaInAsSb layers were 0.05-0.23 and 0.75-0.95, respectively, on GaSb substrates and 0. 23-0.39 and 0.82-0.89, respectively, on InAs substrates. These composi tions correspond to band gap energies of 0.4-0.7 eV. Low-temperature p hotoluminescence (PL) spectra were observed for GaInAsSb layers grown on GaSb and InAs substrates at wavelengths of approximately 1.9 and 2. 0 mu m with half-widths of 20 and 25.3 meV, respectively.