Internal photoinjection and deep level luminescence at ZnSe/GaAs heterointerfaces

Abstract

We have used photoluminescence spectroscopy to measure the relative intensity of the ZnSe and GaAs near band edge ͑NBE͒ emissions at ZnSe/GaAs interfaces fabricated by molecular beam epitaxy under different growth conditions. Using a HeCd laser to excite free electron-hole pairs near the buried heterointerface, we found systematic variations in the NBE relative intensity as a function of the Zn to Se beam pressure ratio used to grow the ZnSe epilayers. The results are in good agreement with the predictions of a simple expression for free carrier injection across the interface due to internal photoemission. In such a process, laser excitation results in free carriers which can move from GaAs to ZnSe over barriers due to the heterojunction band offsets and recombine across the band gap or via deep levels. The variation of such internal photoemission with different growth conditions supports the previously reported dependence of the ZnSe/GaAs band offset on the local interface composition.

Structural and electronic properties of ZnSe/AlAs heterostructures

“…4,5 Such changes were mostly implemented [4][5][6][7] by employing Se-rich or Zn-rich growth conditions during the early stages of interface fabrication by molecular beam epitaxy ͑MBE͒. Early photoemission spectroscopy results obtained in situ on thin-overlayer samples [4][5][6][7] were later systematically confirmed in fully functional heterojunction diodes by internal photoemission 8 and lowtemperature transport measurements. 9,10 These early experimental investigations were guided a priori and put into perspective a posteriori by the parallel development of a whole new theoretical framework for semiconductor heterojunctions.…”