Deep Level Defects in Epitaxial 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 $<$400\r{ }C, making deep level defects a concern. Both GaAs layers and p-i-n structures containing a GaAsBi quantum well in the i-layer having a bismide fraction up to 4.7{\%} were grown by molecular beam epitaxy in the range 285-580\r{ }C. Deep level transient spectroscopy (DLTS) measurements of GaAs layers show several different traps, depending on the doping type and growth temperature, but all in concentration $<$5$\times $10$^{14}$ cm$^{-3}$. Similarly, the DLTS spectra from p-i-n devices vary with the growth conditions and with the bismide fraction and trap concentrations are $<$1$\times $10$^{15}$ cm$^{-3}$. These DLTS results are consistent with strong photoluminescence\footnote{X. Lu, et al., Appl. Phys. Lett. \textbf{95}, 041903 (2009).} and electroluminescence\footnote{R.B.Lewis, et al. J. Crystal Growth \textbf{311}, 1872-75 (2009)} from GaAsBi quantum wells having bismide fraction $\leq$5{\%}. The properties of these traps will be discussed.