Use of tertiarybutylphosphine for OMVPE growth of (Al_xGa_1-x)o.51 In_0.49P

Abstract

This paper reports the results of atmospheric pressure organometallic vapor phase epitaxial growth of (Al _x Ga_1-x )_{0.51 0.49}P thin films using tertiarybutylphosphine (TBP) as the phosphorus source. The trimethylalkyls were used as group III sources. The growth temperature was 680° C. It was observed that V/III ratio dramatically affected the surface morphology and photoluminescence (PL). The epilayers grown at a V/III ratio lower than 60 had rough surfaces and weak PL emission. An input V/III ratio larger than 70 was required to obtain good surfaces and strong PL emission. Good quality (Al_xGa_1-x )_{0.51 0.49}P epilayers forx ≤ 0.62 were obtained at a V/III ratio of 85. The surface morphologies were smooth except for the occurrence of dense oval-shaped hillocks forx > 0.42. The Al distribution coefficient using TBP is the same as for phosphine (PH₃), which was used as the phosphorus source in previous AlGalnP growth. No parasitic reactions between TBP and trimethylalkyls were observed. 10 and 300 K PL emission was observed for all epilayers withx ≤ 0.62. However, the PL peak energy did not follow the band gap, as obtained for (Al_xGa_1-x )_{0.51 0.49}P epilayers grown using PH₃. The PL peak energy at both 10 and 300 K increased with increasingx forx ≤ 0.35, and then became nearly constant with further increases inx. In this region the PL is believed to be from a process involving a deep energy level, induced by an impurity from the TBP, bound to theX conduction band minimum. It was concluded that TBP has the potential to replace PH₃ for OMVPE growth of Al-containing compounds, although the purity needs to be improved.