Growth temperature dependence of self-formation process of quantum dot structures in GaP/InP short-period superlattices grown on GaAs (311)A substrate

Growth temperature dependence of the self-formation process of quantum dot (QD) structures in (GaP)(1.5) (InP)(1.88) short-period superlattices (SLs) grown on GaAs (311)A substrates is studied by scanning tunneling microscopy (STM). SLs are grown by gas-source molecular beam epitaxy (MBE) at 420-500 degrees C. The STM image of the sample grown at 460 degrees C reveals comp letely self-formed QD structures aligned along both [(2) over bar 33] and [ <0(1)over bar>1] directions due to the strain-induced lateral composition m odulation. On the other hand, both below (420 degrees C) and above (480 deg rees C, 500 degrees C) this temperature the self-formation process of QD st ructures is suppressed and only incomplete structures elongated along the [ <0(1)over bar>1] direction are formed, probably due to the suppressed or ov er-enhanced migration of group III atoms on the surface, respectively. Scan ning tunneling spectroscopy (STS) measurements reveal that the amplitude of the lateral periodic variation of the band-gap energy in the self-formed s tructures also decreases both below and above the optimum growth temperatur e.