InGaN Multi-quantum-well Laser Diodes Research Articles

Optically pumped lasing properties of InGaN/GaN stripe multiquantum wells with ridge cavity structure on patterned (001) Si substrates

We demonstrated lasing action and investigated the optical properties of multiquantum-well (MQW) stripe crystals on patterned (001) Si substrates. Longitudinal and higher order transverse modes were observed from a ridge waveguide structure. These results strongly suggest the possibility of fabricating InGaN MQW laser diodes on (001) Si.

Performance and optical gain characteristic of InGaN MQW laser diodes

This paper discusses the performance of InGaN multi-quantum well (MQW) laser diodes and the effects of composition fluctuations on the optical gain characteristics. Pulsed threshold current densities as low as 4.8 kA/cm 2 have been observed for ridge-waveguide laser diodes allowing room-temperature continuous-wave (cw) operation with threshold currents of 125 mA and operating voltages of 6.5 V. The effects of composition fluctuations in the InGaN alloy were investigated by comparing theoretical and experimental gain spectra obtained from true spontaneous emission measurements, cavity length studies and cw laser emission spectra. We find that the distributed losses in our structures are of the order of 45–50 cm −1. Using a simple logarithmic gain–current relationship, we were able to describe the experimental results with a characteristic gain g 0=72 cm −1 and a transparency current density J trans=2.5 kA/cm 2. Optical gain calculations have been performed for InGaN quantum-well structures, based on band structures generated with an effective-mass Hamiltonian and taking pseudomorphic strain into account. We find that a very modest amount of composition fluctuation (standard deviation in the In content <0.008), which produces inhomogeneous broadening, is consistent with the experimental observations. This is consistent with TEM structural studies, which show that there is negligible phase separation in In x Ga 1− x N MQW with indium content smaller than x=0.1.

InGaN/GaN/AlGaN-Based Leds and Laser Diodes

InGaN quantum-well-structure blue LEDs were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. The output power of both LEDs was as high as 6 mW at a current of 20 mA. The LED on sapphire had a considerable amount of leakage current in comparison with that on ELOG. These results indicate that In composition fluctuation is not caused by threading dislocations (TDs), free carriers are captured by radiative recombination centers before they are captured by nonradiative recombination centers in InGaN, and that the dislocations form the leakage current pathway in InGaN. Red LED with an emission peak wavelength of 650 nm was fabricated by increasing the In composition and thickness of InGaN well layer. When the laser diodes (LD) was formed on the GaN layer above the SiO2 mask region, the threshold current density was as low as 3 kAcm−2. When the LD was formed on the window region, the threshold current density was as high as 6 to 9 kAcm−2. There is a possibility that a leakage current due to a large number of TDs caused the high threshold current density on the window region. InGaN multi-quantum-well (MQW) structure LDs grown on the ELOG substrate showed an output power as high as 420 mW under RT-CW operation. The longest lifetime of 9,800 hours at a constant output power of 2 mW was achieved. The InGaN MQW LDs were fabricated on a GaN substrate. The fundamental transverse mode was observed up to an output power of 80 mW.

InGaN-BASED LASER DIODES

▪ Abstract Continuous-wave operation of InGaN multi-quantum-well (MQW) structure laser diodes (LDs) has been demonstrated at room temperature with output power up to 50 mW, operating temperature up to 100°C, emission wavelength of 400–420 nm, and a lifetime up to 300 h. InGaN MQW LDs with a lifetime of more than 1000 h are expected soon. Commercialization will begin in 1998 if research on the bluish-purple InGaN-based laser diodes continues to progress. The stimulated emission of the InGaN-based LDs originates from localized energy states of 100–250 meV depth, which are equivalent to quantum dot energy states, probably arising from from InGaN composition fluctuation in the InGaN well layers.

InGaN/GaN/AlGaN-Based Leds and Laser Diodes

AbstractInGaN quantum-well-structure blue LEDs were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. The output power of both LEDs was as high as 6 mW at a current of 20 mA. The LED on sapphire had a considerable amount of leakage current in comparison with that on ELOG. These results indicate that In composition fluctuation is not caused by threading dislocations (TDs), free carriers are captured by radiative recombination centers before they are captured by nonradiative recombination centers in InGaN, and that the dislocations form the leakage current pathway in InGaN. Red LED with an emission peak wavelength of 650 nm was fabricated by increasing the In composition and thickness of InGaN well layer. When the laser diodes (LD) was formed on the GaN layer above the SiO2 mask region, the threshold current density was as low as 3 kAcm-2. When the LD was formed on the window region, the threshold current density was as high as 6 to 9 kAcm-2. There is a possibility that a leakage current due to a large number of TDs caused the high threshold current density on the window region. InGaN multi-quantum-well (MQW) structure LDs grown on the ELOG substrate showed an output power as high as 420 mW under RT-CW operation. The longest lifetime of 9,800 hours at a constant output power of 2 mW was achieved. The InGaN MQW LDs were fabricated on a GaN substrate. The fundamental transverse mode was observed up to an output power of 80 mW.