Dilute Bismuth Containing W-Type Heterostructures for Long-Wavelength Emission on GaAs Substrates

Energy efficiency, superior performance, and long-term reliability are crucial advantages of GaAs-based semiconductor laser diodes featuring strained type-I quantum wells as active regions. This class of semiconductor structures provides very good performance in the near-infrared spectral range. Achieving longer wavelength emission on GaAs substrates has proven to be difficult so far. Alloys including nitrogen (N) and bismuth (Bi) promise active materials with the possibility to push this accessible emission wavelength range toward the telecommunication bands. The alloys show a drastic decrease in the band-gap energies already for small fractions of the respective elements. However, the strong nonequilibrium nature of such multinary alloys has rendered sufficient incorporation with reasonable material quality impossible so far, mandating alternate approaches. Here, we embed a Ga(As,Bi) quantum well (QW) between two Ga(N,As) QWs in a so-called W-type quantum well heterostructure (WQW). This approach has the potential to achieve significant optical gain due to sufficient wave-function overlap, which is enhanced compared to type-II heterostructures. In particular, we realize WQWs with emission wavelengths around 1.1, 1.3, and 1.4 mu m by drastically altering the growth conditions compared to standard growth conditions established for type-I QW structures. This particularly applies to Bi segregated at the interfaces in the structure. The resulting recipes enable the future growth of tailored WQWs for even longer emission wavelengths, e.g., extending beyond the telecom bands into the fingerprint region in the midinfrared.