INFLUENCE OF PRESSURE ON PHOTOLUMINESCENCE AND ELECTROLUMINESCENCE INGAN INGAN/ALGAN QUANTUM-WELLS/

We have measured photoluminescence and electroluminescence in two diff erent types of high-brightness single-quantum-well light emitting diod es manufactured by Nichia Chemical Industries with InxGa1-xN active la yers (x = 0.45 and x = 0.15), under hydrostatic pressures up to 8 GPa. We discovered that the pressure shift of the primary luminescence pea k in each diode is very small: 12 and 16 meV/GPa for the green and blu e diodes, respectively. The observed pressure coefficients are much lo wer than those characteristic of the energy gap in GaN (approximate to 40 meV/GPa) or the energy gap in InN (approximate to 33 meV/GPa). Thi s kind of behavior is usually associated with recombination processes involving localized states. These localized states may be associated e ither with band tails (arising from In fluctuations in the active laye r or from high density of defects), and/or with localized excitons of various types. (C) 1997 American Institute of Physics.