Effect of growth temperature on defect states of GaNAsSb intrinsic layer in GaAs/GaNAsSb/GaAs photodiode for 1.3µm application
Résumé
A GaAsSbN layer closely lattice matched to GaAs was used as an intrinsic layer (i layer) in a GaAsGaAsSbNGaAs p-i-n photodiode with response up to 1.3 μm. Deep level transient spectroscopy measurement on the GaAsGaAsSbNGaAs reveals two types of hole traps (HTs) in the GaAsSbN i layer; (i) HT1: a shallow N-related defect state (Ea ∼0.10-0.12 eV) and (ii) HT2: an AsGa point defect-related midgap defect state with Ea ∼0.42-0.43 eV. Reduction in growth temperature from 480 to 420 °C reduces the HT2 trap concentration from 4× 1015 to 1× 1015 cm-3, while increases the HT1 trap concentration from 1× 1014 to 7× 1014 cm-3. Reduction in the HT2 trap concentration following growth temperature reduction was attributed to the suppression of AsGa point defect formation. Evidence of possible change of the AsGa midgap state to a shallow level defect due to the formation of (AsGa - NAs) pairs was also suggested to have increased the HT1 trap concentration and reduced the HT2 trap concentration. An ∼4 dBm improvement in photoresponse under 1.3 μm laser excitation and approximately eight times reduction in dark current at -8 V reverse bias were attributed to the reduction in the overall trap concentration and mainly the reduction of the AsGa -related midgap trap concentration in the sample grown at 420 °C.
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