The effects of the growth temperature on Al_xGa_l-xAs (0≤ x ≤0.37) LED materials grown by OM-VPE

Abstract

The epitaxial growth of AlGaAs of LED quality by OM-VPE is achieved either by using high growth temperatures (≥780°C) or by using oxygen gettering methods and low growth temperatures (≤750°C). For 6% AlGaAs, the most studied composition in this work, graphite baffles and a molecular sieve, are used at low growth temperatures (≈680°C) to improve both the normalized PL intensity of epi layers and the EL efficiency of LEDs. Growth at high temperature, however, does not require oxygen gettering methods to achieve the same material quality. The improvement in both cases is achieved by reducing the concentration of the oxygen-related defect that is the source of the 0.8 eV peak, which limits the performance of 6% AlGaAs LEDs. Al_xGa_1−xAs alloys with x≥0.06 also show a similar behavior relative to the growth temperature. The defect peak itself remains invariant with x. This 0.8 eV PL peak is likely to be associated with Al, since the reaction between Al and oxygen is strong and the 0.8 eV peak is seldom observed in GaAs epi layers, regardless of the growth temperature.