Physics

A comparative study of the band-offset ratio of the three competing laser materials, namely InGaAsP/InP, AlGaInAs/InP, and InGaNAs/GaAs, has been undertaken for the first time, to show the usefulness of the strain-compensated quantum wells (QW) from the band alignment point of view. It was confirmed from our calculations that the alternative uncompensated AlGaInAs and InGaNAs laser systems have substantially better band alignment than that of the commonly used uncompensated InGaAsP. The detailed analysis of the effect of strain compensation on the band alignments of the three competing laser materials has shown that strain compensation brings further benefits to the alternative laser systems, especially to InGaNAs/GaAs. Therefore, high temperature operation has been anticipated in these alternative laser systems with a strain compensated barrier due to the better electron and hole confinement as a result of the increased band offset and a more favorable band offset ratio. In addition, the use of GaAsP barriers instead of AlGaAs barriers to provide strain compensation improves the band alignment, even in the uncompensated value of the InGaNAs/GaAs laser system. Moreover, the introduction of strain to the barrier into the InGaNAs/GaAs laser system causes the electron wells to be much deeper than that of the hole wells, which is essential for having good high temperature characteristics. Therefore, a strain-compensated InGaNAs/GaAs laser system can be offered as an ideal candidate for high temperature operation. PACS numbers: 73.21.Fg, 42.55.Px, 42.60.Mi

The aim of this work is to examine the effect of dilute nitride and/or antimonite on the critical layer thickness of GaInAs quantum wells on GaAs and InP substrates by means of Matthews and Blakeslee force model. The study provides a comparison of the critical layer thickness of the related GaIn(N)As(Sb) QWs in (001) and (111) orientation. Our calculations indicate the importance of antimonite and the proper usage of it with dilute nitrides in order to tailor the active layer thickness and emission wavelength of quantum well laser devices.

In order to achieve good high temperature laser performance, it is essential to have very deep electron wells. InGaAs system on GaAs substrate suffers from poor temperature characteristics due to the electron overflow over the rather small conduction band offset. By means of the Harrison's model, we investigate the effect of the strain compensation on band alignments of InGaAs/GaAs laser system and show that strain compensation improves the band alignments of this laser system. The use of GaAsP or InGaP barrier instead of GaAs barrier results the strain-compensated laser system having better band alignment than that of the conventionally strained InGaAs. Therefore, high temperature operation has been anticipated in these laser systems with strain compensated barriers due to better electron and hole confinement as a result of the increased band offset and a more favorable band offset ratio. r

Hot electron light emission and lasing in semiconductor heterostructure (Hellish) devices are surface emitters the operation of which is based on the longitudinal injection of electrons and holes in the active region. These devices can be designed to be used as vertical cavity surface emitting laser or, as in this study, as a vertical cavity semiconductor optical amplifier (VCSOA). This study investigates the prospects for a Hellish VCSOA based on GaInNAs/GaAs material for operation in the 1.3-μm wavelength range. Hellish VCSOAs have increased functionality, and use undoped distributed Bragg reflectors; and this coupled with direct injection into the active region is expected to yield improvements in the gain and bandwidth. The design of the Hellish VCSOA is based on the transfer matrix method and the optical field distribution within the structure, where the determination of the position of quantum wells is crucial. A full assessment of Hellish VCSOAs has been performed in a device with eleven layers of Ga 0.35 In 0.65 N 0.02 As 0.08 /GaAs quantum wells (QWs) in the active region. It was characterised through I-V, L-V and by spectral photoluminescence, electroluminescence and electro-photoluminescence as a function of temperature and applied bias. Cavity resonance and gain peak curves have been calculated at different temperatures. Good agreement between experimental and theoretical results has been obtained.

We investigate the effect of doping on the parameters of transparency carrier density and peak gain of GaInNAs/GaAs quantum well lasers emitting at 1.3 µm and compare the results with that of an equivalent nitrogen-free InGaAs/GaAs structure. A significant reduction in the transparency carrier density by p-type doping and an increase in gain by n-type doping are observed for GaInNAs/GaAs contrary to nitrogen-free InGaAs/GaAs. The results are analysed using the band-anti-crossing model for band gap, effective mass and simple approximate expressions for carrier density and optical gain. Our calculations show that doped III-N-V quantum well active layers may have certain benefits to lasers.

The research on dilute bismuth containing III-V semiconductor alloys and its applications are studied. These alloys are obtained by incorporating a small amount of Bi in the host semiconductor. The presence of Bi reduced the energy bandgap of the alloys. The bandgap and optical properties of InAs 1− Bi , InP 1-x Bi x, and InSb 1− Bi alloy systems are investigated for optoelectronic devices. The optical properties of semiconductors are important to change the properties of device performance. The refractive index strongly depends on the direct bandgap of the semiconductor alloys. The bandgap of the In-V-Bi semiconductor layer can be engineered by means of adding bismuth into InAs, InP, InSb. In this work, the refractive indices and the optical parameters of the In-V-Bi alloys are investigated.