Optical properties in InGaN/GaN multiple quantum wells and blue LEDs

InGaN/GaN multiple quantum wells (MQW) and blue MQW light-emitting diodes were grown by metalorganic vapor phase epitaxy (MOVPE). Band gap narrowing of the PL spectra for the InGaN/GaN MQW LEDs can be observed at room temperature. In addition, the emission wavelength of EL and PL spectra for the MQW blue LEDs exhibits a blue-shift phenomenon when increasing the injection current and laser power, respectively. This luminescence behavior can tentatively be understood as a competition between a spectral red-shift mechanism of piezoelectricity-induced quantum-confined Start effect (PQCSE) and a blue-shift mechanism of band-filling and charge screening effects. Blue MQW LEDs emitting at 465 nm have been successfully fabricated with a narrow FWHM of about 30 nm at 20 mA. The output power of bare chips is better than 1 mA at 20 mA and the forward voltages are less than 3.8 V.