Spectra and quantum efficiency of light-emitting diodes based on GaN heterostructures with quantum wells

Spectra and quantum efficiency eta(e) of green LEDs based on heterostructur es InGaN/AlGaN/GaN with multiple quantum wells were studied at currents J = 10(-6) to 10(-1) A. Minor differences in eta(e) (of +/-10% at J approximat e to 10 mA) are caused by sufficiently different distributions of effective charges in the space charge regions and the different role of tunnel compo nent of J at low voltages. The main peak in the spectra at low J (h omega(m ax) = 2.35 to 2.36 eV) does not depend on the voltage. At J > 0.2 mA the sp ectral band is shifted with J (h omega(max) = 2.36 to 2.52 eV). The origin of the "standing" and "moving" bands is discussed. The model of 2D structur es with band tails describes the spectral form with four fitting parameters rather well. A tunnel radiation band is revealed in the long wavelength ra nge (1.93 to 2.03 eV) in the LEDs with a thin space charge region (w less t han or equal to 120 nm). The dependence of eta(e) on J has a maximum which correlates with the fitting parameters and J(V) and N-A(w) curves. Possible microscopic and macroscopic inhomogeneities in the structures are discusse d.