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Deep Impurities in AlGaAs Grown by MOCVD Using Different Hydrogen and Nitrogen as Carrier Gases

A study was carried out to characterize the deep impurities in Al x Ga 1-x As grown by metal-organic chemical vapor deposition (MOCVD) using different carrier gases. Since Al x Gai 1-x As is very sensitive to any impurities, especially moisture and oxygen, in the growth process, the concentration of impurities in Al x Gai 1-x As can serve as a measure of the purity of carrier gases. The undoped AlGaAs layers grown by using H 2 have n-type background concentrations from 3×10 15 to 10×10 15 /cc. The concentrations of oxygen-related traps (E c −0.53 and 0.7 eV) are 0.2−9×10 13 and 3.4−5×10 14 /cc for Pd- and Li-purified H 2 , respectively. Low-temperature photoluminescence (PL) measurements show better PL efficiency in samples grown by using Pd- purified H 2 . Al x Ga 1-x As grown by using N 2 is p-type (p∼6×10 16 /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 H 2 . The memory effect due to impurities from carrier gas left in source materials is also studied.