The emission spectrum of a current injected InGaN/AlGaN surface emitting diode has been investigated. A clear redshift of the low energy edge with increasing injected current has been observed, and is attributed to the many body effects. The carrier density and band gap narrowing are obtained by fitting the line shape of the emission spectrum, using Landsberg model which includes many body effects. A redshift of around 92 meV of the low energy edge is obtained as injected current increases from 400 to 4000 mA. The band gap change can be described well in proportion to the 1/3 power of the carrier density, which is just suggested by the exchange energy of electron–electron, and hole–hole interactions. ©1997 American Institute of Physics.