Improved compositional uniformity of InGaAsP grown by low pressure metalorganic vapor phase epitaxy using tertiary butyl phosphine as the phosphorus source

Abstract

We present the results of an investigation of the effect of group V precursor on the compositional uniformity of InGaAsP (λ = 1.35 μm) layers grown by low pressure metalorganic vapor phase epitaxy on 50 mm diameter substrates. The usual hydride precursors, AsH 3 and PH 3, 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 In 1− x Ga x As y P 1− y films. It was found t hat the value of x varied by ∼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 AsH 3 + PH 3 and TBAs + TBP source combinations to 1% for the AsH 3 + TBP source combination. This corresponded to a decrease in photoluminescence wavelength variation of 30 nm for the AsH 3 + PH 3 combination to 10 nm for the AsH 3 + TBP combination. Furthermore, it was found that the V/III ratio at which specular surfaces could be attained decreased from ∼80 in the case of AsH 3 + PH 3 to <20 with either AsH 3 + TBP or TBAs + TBP and that the relative P incorporation increased in the source combination sequence of AsH 3 + PH 3 <TBAs + TBP < AsH 3 + TBP.