Deep level transient spectroscopy measurements of GaAsBi/GaAs

Bismuth incorporation in GaAs produces a much larger reduction in the band gap than In or Sb alloying, for the same increase in lattice constant. However, Bi is incorporated only at growth temperatures (Tg) < 400 ⁰C, making deep level defects a concern. GaAsBi layers, GaAs layers and p-i-n structures having a 50 nm GaAsBi quantum well with bismide fraction ≤ 5% in the center of the intrinsic layer were grown by molecular beam epitaxy in the temperature range 285-580 ⁰C. Deep level transient spectroscopy (DLTS) measurements of GaAsBi and GaAs Schottky diodes show several different traps. Similarly, DLTS spectra from the p-i-n devices vary with the growth conditions and the bismide fraction. The trap concentrations were found to be ≤ 51015 cm-3, consistent with reported photoluminescence and electroluminescence measurements of the GaAsBi p-i-n structures. The possible identity of some of the traps is discussed.