Spontaneous Emission and Characteristics of Staggered InGaN Quantum-Well Light-Emitting Diodes

Abstract—A novel gain media based on staggered InGaN quantum wells (QWs) grown by metal–organic chemical vapor deposition was demonstrated as improved active region for visible light emitters. Fermi’s golden rule indicates that InGaN QW with step-function like In content in the well leads to significantly improved radiative recombination rate and optical gain due to increased electron–hole wavefunction overlap, in comparison to that of conventional InGaN QW. Spontaneous emission spectra of both conventional and staggered InGaN QW were calculated based on energy dispersion and transition matrix element ob-tained by 6-band formalism for wurtzite semiconductor, taking into account valence-band-states mixing, strain effects, and polarization-induced electric fields. The calculated spectra for the staggered InGaN QW showed enhancement of radiative recombi-nation rate, which is in good agreement with photoluminescence and cathodoluminescence measurements at emission wavelength regime of 425 and 500 nm. Experimental results of light-emitting diode (LED) structures utilizing staggered InGaN QW also show significant improvement in output power. Staggered InGaN QW allows polarization engineering leading to improved luminescence intensity and LED output power as a result of enhanced radiative recombination rate. Index Terms—Gain media, III–nitride, InGaN quantum wells (QWs), light-emitting diodes (LEDs), polarization field engi-neering. I