David Uhl

Lasing characteristics of InAs quantum-dot lasers on (001) InP substrate

Single-stack InAs self-assembled quantum-dot (QD) lasers based on (001) InP substrates have been grown by metalorganic vapor-phase epitaxy. The narrow ridge waveguide lasers lased up to 260 K in continuous-wave operation, and near room temperature in pulsed mode, with emission wavelengths between 1.59 to 1.74 μm. Above 200 K, a very low wavelength temperature sensitivity of 0.09 nm/K was observed. Lasing spectra at different temperatures suggests that the ground states and the excited states almost overlap, and form a quasicontinuous band due to the large size of the InAs dots and their inhomogeneous broadening. These results will provide guidance for further development of long wavelength InAs QD lasers based on InP substrates.

Room-temperature continuous-wave operation of InAsSb quantum-dot lasers near 2 μm based on (001) InP substrate

Single-stack InAsSb self-assembled quantum-dot lasers based on (001) InP substrate have been grown by metalorganic vapor-phase epitaxy. The narrow ridge waveguide lasers lased at wavelengths near 2 μm up to 25 °C in continuous-wave operation. At room temperature, a differential quantum efficiency of 13% is obtained and the maximum output optical power reaches 3 mW per facet with a threshold current density of 730 A/cm2. With increasing temperature the emission wavelength is extremely temperature stable, and a very low wavelength temperature sensitivity of 0.05 nm/°C is measured, which is even lower than that caused by the refractive index change.

Self-assembled InAsSb quantum dots on (001) InP substrates

Self-assembled InAsSb quantum dots (QD) on (001) InP substrates have been grown using metalorganic vapor phase epitaxy. The dot density and size are found to be strongly dependent on the presence of arsine. Direct deposition of InSb on InP and GaSb substrates formed large islands of InSb with low density of less than 5×109/cm2, however, InAsSb QDs of density as high as 4×1010/cm2 could be self-assembled by alternating group III and group V precursors, and high density almost pure InSb QDs were achieved on In0.53Ga0.47As/InP. The formation of high density InAsSb QDs is a result of a local nonequilibrium process and a reduction in mobility of In adatoms on the growth surface due to the presence of arsenic atoms, and in the case of high density almost pure InSb QDs on InGaAs/InP, the InAs interface layer is believed to be responsible. Photoluminescence shows that InSb QDs emit light at room temperature in the range of 1.7–2.2 μm.

Effect of thin GaAs interface layer on InAs quantum dots grown on InGaAs/InP using metalorganic vapor phase epitaxy

InAs self-assembled quantum dots (QDs) embedded within an InGaAs quantum well have been grown on InP substrate by low-pressure metalorganic vapor phase epitaxy. We find out that the underlying InGaAs layer could affect the dot growth dramatically in terms of size distribution and luminescence efficiency. After inserting a thin GaAs interface layer between the underlying InGaAs and the InAs QD layer, improved dot size uniformity and strong room temperature photoluminescence (PL) up to 2 μm were observed. In the case of InAs QDs with no GaAs layer, one has to reduce InAs QD layer thickness in order to obtain room temperature PL. These results suggest that InAs from the underlying InGaAs layer contribute to the InAs QD formation, and cause the InAs QDs to be non-uniform, but a thin GaAs interface layer could effectively block the migration of In atoms from the InGaAs layer toward InAs QDs, and therefore lead to more uniform QD formation with better luminescence efficiency.

Quantum dot/substrate interaction in InAs/In0.53Ga0.47As/InP(001)

InAs quantum dots grown on In0.53Ga0.47As/InP(001) substrate by low-pressure metalorganic chemical vapor deposition were investigated using high-angle annular dark-field imaging. Results suggest significant mass transport of mainly the large-sized component (InAs) from the In0.53Ga0.47As substrate to InAs quantum dots, an unexpected process that increases the system strain energy. The amount of the transported mass increases with quantum dot size. Two monolayers of GaAs inserted between InAs islands and the InGaAs substrate appears to block or at least effectively slow down this mass transport process.

2 /spl mu/m InAsSb quantum-dot lasers

High-density InAsSb quantum dots (QD) have been grown on [001] InP substrates using metalorganic vapor phase epitaxy. Photoluminescence shows the QDs emit light in the range of 1.7-2.2 /spl mu/m at room temperature, and at 2 /spl mu/m the QDs have luminescence 3 times stronger than that of InAs QDs. Narrow ridge lasers based on a single-stack InAsSb QDs were demonstrated near 2 /spl mu/m in cw operation at room temperature with a threshold current density of 730 A/cm/sup 2/, output power of 3 mW/facet and a differential quantum efficiency of 13%.

Improved dot size uniformity and luminescence of InAs quantum dots on InP substrate

InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. We find out that the underlying InGaAs layer could affect the dot growth dramatically in terms of size distribution and luminescence efficiency. After inserting a thin GaAs interface layer between the underlying InGaAs and the InAs QD layer, improved dot size uniformity and strong room temperature photoluminescence up to 2 /spl mu/m were observed. The results suggest that InAs from the underlying InGaAs layer contribute to the InAs QD formation, and cause the InAs QDs to be non-uniform, but a thin GaAs interface layer could effectively block the migration of In atoms from the InGaAs layer toward InAs QDs, and therefore lead to more uniform QD formation with better luminescence efficiency.