FORMATION OF INTERFACE LAYERS IN GAXIN1-XAS/INP HETEROSTRUCTURES - A REEVALUATION USING ULTRATHIN QUANTUM-WELLS AS A PROBE

We have studied the metalorganic vapor phase epitaxy growth of ultrathin GaInAs/InP and GaAs/InP quantum well (QW) structures using photoluminescence (PL) spectra as a probe for interface effects. In parallel we have also studied InAsxP1-x ''interface QWs'' formed by simply exposing InP to AsH3. We see a correlation between QW properties (PL peak position, effective thickness, PL half-width) and the surface phase during the growth of the QW material. For GaAs QWs grown under conditions where typically the As-excess c(4X4)/d(4X4)- or (1X2)-like (with As double layers) surface reconstructions, we find a strong red-shift of the PL peak positions. The red-shift becomes smaller the closer the growth conditions come toward the border to the (2X4) reconstruction (with only one As-termination layer). We thus conclude that the surface itself is one source for As carryover. For GaInAs QWs a boundary between an As-excess/no As-excess surface reconstruction seems to exist at higher AsH3/lower T values. Near to this border GaInAs QWs can be deposited which show PL-half-widths between 7 and 11 meV even for the range of 1-5 ML nominal thickness. The P/As replacement reaction at the lower interface is for short AsH3 interaction times (less than or equal to 1 s) restricted to less than 1 ML and contributes a relatively constant amount to the effective thickness of the QW. Similarly, we show that InAsxP1-x interface QWs formed by short time interaction of InP and AsH3, originate less from a reaction into the depth of the InP, but more from a consumption of the As which is adsorbed onto the InP surface after the AsH3 treatment.