Effect of epitaxial layer thickness on the deep level defects in MBE grown n‐type Al0.33Ga0.67As

The effect of the epitaxial layer thickness on the deep level defects in MBE grown n-Al0.33Ga0.67As is investigated for the first time using current-voltage-temperature (I-V-T), deep level transient spectroscopy (DLTS) and Laplace DLTS techniques. The epitaxial layer thickness is found to have profound effects on the room temperature I-V characteristics, the number of defects detected by DLTS and their concentrations. In this investigation we compare n-Al0.33Ga0.67As samples having epitaxial layer thicknesses of 2 µm and 1.5 µm. Our results reveal that by increasing the layer thickness (1) the reverse current increases; (2) the number of electrically active deep defects increases from two to six; (3) the concentration of the traps increases. The I-V-T and DLTS measurements carried out from 20 K to 300 K show that there is a dominant trap with an activation energy of ∼0.48 eV in both samples but with different concentrations (8.59 × 1014cm-3 and 1.48 × 1014 cm-3 for 2 µm and 1.5 µm samples, respectively). The reduction in the reverse current is directly related to the number of defects and their concentration. Our findings have important implications on the performances of electronic and optoelectronic devices. An attempt to explain the effect of the layer thickness on the deep traps in n-Al0.33Ga0.67As will be given (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)