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

The optical properties of luminescence centres in silicon

Blueshifts in the photoluminescence emission energies from an ensemble of self-assembled InAs quantum dots are observed as a result of postgrowth thermal annealing. Enhancement of the integrated photoluminescence emission and narrowing of the full width half-maxima (from 55 to 12 meV) occur together with blueshifts up to 300 meV at annealing temperatures up to 950 °C. Evidence that the structures remain as dots comes form the observation of level filling and photoluminescence excitation studies which reveal LO phonon peaks occurring at multiples of ∼30 meV from the detection energies.

Tuning self-assembled InAs quantum dots by rapid thermal annealing

The physical properties of GaSb are briefly presented and the device implications reviewed. GaSb is a direct gap semiconductor (0.72 eV) capable of being doped either p or n type with good mobilities and it has significant electro-optical potential in the near IR range. As a substrate, or active layer, GaSb can be employed in conjunction with many semiconductors such as (AlGa)Sb or In(AsSb) and has interesting heterojunction potential for detectors and lasers and quantum well structures.

Gallium antimonide device related properties

It is pointed out that a widely used simple formula may give rise to serious errors in profiling deep level concentrations from capacitance transient experiments. A correction formula is derived based on the space‐charge analysis.

On the determination of the spatial distribution of deep centers in semiconducting thin films from capacitance transient spectroscopy

Defect concentrations in AlxGa1−xSb which is in equilibrium with a liquid phase are calculated. When the liquid phase is Ga rich, a Ga antisite (Ga2−Sb) or an Al antisite (Al2−Sb) is dominant, and the concentrations of vacancies are much smaller than the antisite concentrations. Ga2−Sb is dominant in GaSb equilibrated with a Sb‐rich solution, but the concentration of Sb antisites comes close to that of Ga2−Sb as temperature is lowered. For x larger than 0.6, a group‐III vacancy is the predominant defect in the case of Sb‐rich solutions. Calculated net acceptor concentrations agree well with those determined experimentally. A complex defect composed of GaSb and a Ga vacancy, which have been taken as the dominant residual acceptor, is expected to be negligible.

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Native defects in the AlxGa1−xSb alloy semiconductor

The n‐type silicon crystals of about 0.15, 0.9, and 10 Ω cm (pulled material) and 120 Ω cm (float‐zone material) are exposed to 2–9‐MeV electron beams at total integrated fluxes up to about 1018 electrons/cm2. The production rates of each complex defect in irradiated silicon are investigated. They are obtained from the condition of charge neutrality by using the experimental values of the resistivity as a function of bombardment dose. The electron energy dependence and the impurity density dependence of the production rate are determined for each complex defect. The results suggest that a configuration of the defect states at Ec−0.3 eV may be associated with a phosphorus atom, and in the intrinsic region the two occupied and vacant states should be symmetrically located above and below the middle of the energy gap, respectively.

Complex defects introduced into Si by high‐energy electron irradiation: Production rates of defects in n‐Si

Effects of rapid thermal processing (RTP) using halogen lamps on GaAs with 50‐, 200‐, and 1250‐nm‐thick SiO2 encapsulants have been studied by capacitance‐voltage, secondary‐ion‐mass spectroscopy, and x‐ray photoelectron spectroscopy. RTP has been performed at 760 and 910 °C for 9 s. A decrease of the carrier concentration is observed near the SiO2/GaAs interface in all RTP samples. The decreased carrier concentration profile is fitted to a complementary error function diffusion profile. This indicates that the decrease of the carrier concentration by RTP is related to the Ga out‐diffusion through SiO2. Furthermore, the amount of the decreased carrier concentration is found to be proportional to the doped Si concentration. These results show that the origin of the carrier concentration decrease is the formation of VGa‐SiGa complex defects called the self‐activated center. The amount of the Ga out‐diffusion is larger in the RTP samples at 760 °C with thicker SiO2 and at 910 °C with a thinner one. This inverse relation can be explained by taking account of two different kinds of driving force, that is, interfacial thermal stress and the interfacial reaction between GaAs and SiO2. Interfacial thermal stress enhances the Ga out‐diffusion in RTP at 760 °C, while interfacial reaction enhances in RTP at 910 °C through As loss.

Ga out‐diffusion in rapid‐thermal‐processed GaAs with SiO2 encapsulants

We report Raman spectra of cubic ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$S grown by metalorganic vapor-phase epitaxy and metalorganic molecular-beam epitaxy on (001) GaAs substrates. Two longitudinal-optical (LO) modes and one transverse-optical mode are observed, and their behavior is similar to that of the one-mode type. However, the signal intensity of the lower-frequency LO phonon is strong compared with that in hexagonal ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$S, which exhibits a typical one-mode behavior. We also observe two additional peaks that are tentatively attributed to disorder-activated modes.

Raman spectra of cubic Zn1-xCdxS.

Rapid thermal processing (RTP) using halogen lamps for liquid encapsulated Czochralski grown GaAs doped with Si has been studied by deep‐level transient spectroscopy, capacitance‐voltage, and photoluminescence measurements. RTP is performed at 700, 800, and 900 °C for 6 s with and without SiO2 encapsulation. Three electron traps ED1(Ec −0.26 eV), ED2(Ec −0.49 eV), and ED3(Ec −0.55 eV) are produced depending on RTP conditions. The trap ED1 is observed in all RTP samples, and its depth profiles vary with RTP conditions. The decrease of the shallow donor concentration occurs for RTP samples above 800 °C, especially for those without encapsulation. It is thought that these results, which are peculiar to the RTP method, are related to the production of As interstitials and As vacancies by the large thermal stress induced by the rapid heating for RTP. The decrease of the concentration of trap EL2(Ec −0.81 eV) is not observed with RTP as reported in the furnace processing. This is due to the effect of the short‐time processing of RTP.

Takao Wada

Papers

Native defects in the AlxGa1−xSb alloy semiconductor

Complex defects introduced into Si by high‐energy electron irradiation: Production rates of defects in n‐Si

Ga out‐diffusion in rapid‐thermal‐processed GaAs with SiO2 encapsulants

Raman spectra of cubic Zn1-xCdxS.

Variations of electron traps in bulk n‐GaAs by rapid thermal processing