IMPROVED COMPOSITIONAL UNIFORMITY OF INGAASP GROWN BY LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY USING TERTIARY BUTYL PHOSPHINE AS THE PHOSPHORUS SOURCE

We present the results of an investigation of the effect of group V precursor on the compositional uniformity of InGaAsP (lambda = 1.35 mum) layers grown by low pressure metalorganic vapor phase epitaxy on 50 mm diameter substrates. The usual hydride precursors, AsH3 and PH3, and their organometallic counterparts, tertiary butyl arsine (TBAs) and tertiary butyl phosphine (TBP) were used in a variety of combinations. Lattice mismatch and photoluminescence mapping of the wafers were used to calculate the values of x (Ga mole fraction) and y (As mole fraction) in the resulting In1-xGaxAsyP1-y films. It was found that the value of x varied by approximately 1% across the wafer area for all group V source combinations but that the variation in the value of y improved from 2.8 -2.9% for both the AsH3 + PH3 and TBAS + TBP source combinations to 1% for the AsH3 + TBP source combination. This corresponded to a decrease in photoluminescence wavelength variation of 30 nm for the AsH3 + PH3 combination to 10 nm for the AsH3 + TBP combination. Furthermore, it was found that the V/III ratio at which specular surfaces could be attained decreased from approximately 80 in the case of AsH3 + PH3 to < 20 with either AsH3 + TBP or TBAs + TBP and that the relative P incorporation increased in the source combination sequence of AsH3 + PH3 < TBAs + TBP < AsH3 + TBP.