BAND-GAP BOWING IN GAP1-XNX ALLOYS

The interband optical absorption edge of GaP1-xNx alloys grown by molecular beam epitaxy has been investigated by photoluminescence and photoluminescence excitation (PLE) spectroscopy. The results demonstrate the transition from nitrogen-bound exciton luminescence indicative of isoelectronic traps in lightly doped films of GaP:N to the formation of indirect band gap alloys in the heavily N-doped GaP films. A large red shift or reduction in band gap energy with increasing N concentration which is observed in PLE spectroscopy identifies the GaP1-xNx alloy system as one of the limited number of alloy systems whose intermediate compositions can have band gaps smaller than those of either of the constituent binary compounds.