Recent advances in nonsilica fiber technology have prompted the development of suitable materials for devices operating beyond 155 mu m The III-V ternaries and quaternaries (AlGaIn)(AsSb) lattice matched to GaSb seem to be the obvious choice and have turned out to be promising candidates for high speed electronic and long wavelength photonic devices Consequently, there has been tremendous upthrust in research activities of GaSb-based systems As a matter of fact, this compound has proved to be an interesting material for both basic and applied research At present, GaSb technology is in its infancy and considerable research has to be carried out before it can be employed for large scale device fabrication This article presents an up to date comprehensive account of research carried out hitherto It explores in detail the material aspects of GaSb starting from crystal growth in bulk and epitaxial form, post growth material processing to device feasibility An overview of the lattice, electronic, transport, optical and device related properties is presented Some of the current areas of research and development have been critically reviewed and their significance for both understanding the basic physics as well as for device applications are addressed These include the role of defects and impurities on the structural, optical and electrical properties of the material, various techniques employed for surface and bulk defect passivation and their effect on the device characteristics, development of novel device structures, etc Several avenues where further work is required in order to upgrade this III-V compound for optoelectronic devices are listed It is concluded that the present day knowledge in this material system is sufficient to understand the basic properties and what should be more vigorously pursued is their implementation for device fabrication (C) 1997 American Institute of Physics

The physics and technology of gallium antimonide: An emerging optoelectronic material

Photoluminescence in InGaAs/GaAs strained‐layer quantum wells is strongly quenched by temperatures above 10–100 K, depending on the well width. Analysis of this dependence shows that the quenching mechanism is thermal activation of electron‐hole pairs from the wells into the GaAs barriers, followed by nonradiative recombination through a loss mechanism in bulk GaAs. The addition of Al to the barriers to improve confinement eliminates loss through this route but introduces another loss mechanism, characterized by an activation energy independent of well width and with a smaller pre‐exponential factor.

Thermal quenching of the photoluminescence of InGaAs/GaAs and InGaAs/AlGaAs strained-layer quantum wells

GaSb photovoltaic cells are the most common choice for receivers in thermophotovoltaic (TPV) systems. Although nowadays their manufacturing technology is well established, a theoretical simulation frame for their modelling under real TPV operating conditions is still not fully developed. This is basically due to the lack of a reliable and accurate set of GaSb material parameters as input for the semiconductor simulation tools. Thorough GaSb TPV cell models are needed to understand the electro-optical behaviour of the cells and eventually are essential in improving their design. This work will try to go beyond this key issue, carefully analysing and reviewing some of the key parameters for GaSb. A complete set of material parameters, including revised values for the intrinsic concentration, the electron and hole mobilities and the absorption coefficient, is given based on extended reviews of previously published data. For the first time, estimations for their temperature dependences are introduced. Finally, GaSb TPV cells are manufactured and characterized inside a real TPV system prototype. The comparisons between the electrical measurements and the model theoretical predictions confirm the validity of the proposed set of GaSb material parameters and their temperature dependences.

Temperature-dependent GaSb material parameters for reliable thermophotovoltaic cell modelling

The temperature dependence of photoluminescence from the high‐quality unintentionally doped GaSb layers grown by liquid‐phase epitaxy has been studied. The epitaxial layers grown at temperatures above 590 °C, from the Ga‐ or Sb‐rich solutions, reproducibly have a low‐carrier concentration of 6–8×1015 cm−3 and exhibit p‐type conduction. But it gives n type as grown from the Ga‐rich solution at 360 °C. For the samples grown from the Ga‐rich solutions, the 16 K photoluminescence spectrum is dominated by the partially resolved lines related to the transitions of excitons bound to donors and neutral acceptors. The acceptor‐related band (777.8 meV) which is always presented in the GaSb material due to the native lattice defects has been much reduced as compared to the exciton‐related lines. Especially for the n‐type samples grown at low temperatures (360 °C), the ratio of the emission intensity from the exciton‐related lines to that from the acceptor‐related band is 10. For the samples grown from the Sb‐rich so...

Photoluminescence of high-quality GaSb grown from Ga- and Sb-rich solutions by liquid-phase epitaxy

Low-temperature photoluminescence of epitaxial GaSb grown by MOVPE from TMGa and TMSb on various substrates is studied and compared with existing results for GaSb grown by other techniques. The effects of growth conditions are considered. It is found that a growth temperature of 650 degrees C is too high, and the layers are of very poor quality, while below the optimum temperature of 600 degrees C the growth rate slows, although the optical quality appears unaffected. Investigations into the range of III/V ratios over which good quality material could be grown indicated that this factor was more critical for GaSb than for GaAs; Sb-rich conditions produced samples with poor radiative efficiency, while samples grown under Ga-rich conditions were covered in excess Ga droplets. In addition, the authors found that, in common with other growth techniques, the concentration of the native defect in GaSb could be controlled using the III/V ratio, and an excellent correlation was found between electrical results and features in the photoluminescence spectra. For layers not lattice-matched to the substrate, the spectrum is red-shifted. They surmise that this is due to differential thermal contraction of the epilayer and substrate. A homoepitaxial sample was chosen for detailed study and from the dependence of the spectra on temperature and excitation intensity, a previously observed bound exciton was confirmed and an acceptor of 15 meV binding energy was found.

Photoluminescence of GaSb grown by metal-organic vapour phase epitaxy

The authors report a characterisation study of single epitaxial layers of GaSb grown by the technique of molecular beam epitaxy (MBE). Both optical and electrical properties of this material are determined by low-temperature photo-luminescence and Hall effect techniques respectively, and compared with previous work on bulk GaSb grown by other methods. Optically detected cyclotron resonance (ODCR) measurements are reported for the first time in this material in order to determine conduction band electron effective masses and carrier momentum relaxation times. Deduced electron mobilities obtained by this novel technique are of the order of 105 cm2V-1s-1 and are in close agreement with theory.

http://iopscience.iop.org/article/10.1088/0268-1242/3/12/002/pdf

Optical, Hall and cyclotron resonance measurements of GaSb grown by molecular beam epitaxy

In this letter, photoluminescence results obtained from two different undoped multilayered pseudomorphic structures grown by molecular beam epitaxy are compared. Intense and spectrally narrow emission was observed from both GaAs/InxGa1−xAs/GaAs and AlxGa1−xAs/InxGa1−xAs/GaAs structures. Excitonic emission from the quantum wells was confirmed by measurements of photoluminescence excitation spectra. The intensity and temperature dependences of the photoluminescence also revealed emission arising from bound excitons and impurities in the quantum wells. Intrinsic and extrinsic emission from confined levels was confirmed by the recorded photoluminescence excitation spectra along with intensity and temperature dependences. In the asymmetric AlxGa1−xAs/InxGa1−xAs/GaAs structure large changes were observed in the photoluminescence intensity under continuous optical excitation which are caused by the optical excitation of defects in the ternary AlxGa1−xAs on top of the pseudomorphically grown InxGa1−xAs.

P. B. Kirby

Papers

Optical, Hall and cyclotron resonance measurements of GaSb grown by molecular beam epitaxy

Photoluminescence study on undoped single quantum well pseudomorphic structures