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Published online by Cambridge University Press: 26 February 2011
A study was carried out to characterize the deep impurities in AlxGa1-x As grown by metal-organic chemical vapor deposition (MOCVD) using different carrier gases. Since AlxGai1-x As is very sensitive to any impurities, especially moisture and oxygen, in the growth process, the concentration of impurities in AlxGai1-xAs can serve as a measure of the purity of carrier gases. The undoped AlGaAs layers grown by using H2 have n-type background concentrations from 3×1015 to 10×1015/cc. The concentrations of oxygen-related traps (Ec−0.53 and 0.7 eV) are 0.2−9×1013 and 3.4−5×1014/cc for Pd- and Li-purified H2, respectively. Low-temperature photoluminescence (PL) measurements show better PL efficiency in samples grown by using Pd- purified H2. AlxGa1-xAs grown by using N2 is p-type (p∼6×1016/cc) with an oxygen-related trap and two hole traps. The concentration of oxygen-related trap is more than one order of magnitude higher than that of AlGaAs using Pd-purified H2. The memory effect due to impurities from carrier gas left in source materials is also studied.