Improved structure and performance of the GaAsSb/InP interface in a resonant tunneling diode

GaAsSb/InP(1 0 0) hetero-interfaces were studied with regard to the performance of metal organic chemical vapor deposition (MOCVD)-grown p-type resonant tunneling diodes (RTDs). For that, thin InP layers were grown by MOCVD on the ternary compound GaAs0.5Sb0.5, which is lattice-matched to InP(1 0 0). Two different surface reconstructions of (1 0 0) GaAs0.5Sb0.5, similar to a reconstruction of either (1 0 0) GaAs or (1 0 0) GaSb, were used for preparing the InP/GaAs0.5Sb0.5 hetero-interfaces: the As-rich, c(4×4) and the Sb-rich, (1×3) reconstructions. The preparation of the RTDs was identical except for the Sb- versus As-rich reconstruction of GaAsSb. The RTDs with As-rich prepared GaAsSb/InP interfaces showed significantly more symmetric I–V characteristics than those with the Sb-rich interface preparation, demonstrating a clear advantage for the As-rich interface preparation. Surfaces were measured in-situ with reflectance difference spectroscopy (RDS) and analyzed in ultrahigh vacuum (UHV) with low-energy electron diffraction (LEED) with regard to the sharpness of the interface. The RD spectra of thin hetero-epitaxial InP layers grown on GaAsSb (1 0 0) were compared to the well-established RD spectrum of MOCVD-prepared homo-epitaxial, (2×1)-like reconstructed P-rich InP (1 0 0), that was used as reference for a well-defined surface. Growing InP on the c(4×4) reconstructed GaAsSb (1 0 0) surface resulted in a significantly sharper interface than InP growth on (1×3) reconstructed GaAsSb(1 0 0), a result that was also borne out by high-resolution X-ray diffraction spectra.