Nobuhiko Noto

Characterization of AiGaP/GaP Heterostructures Grown by MOVPE

Abstract High quality Al x Ga 1- x P/GaP heteroepitaxial layers were grown by a barrel-type multiwafer metalorganic vapor phase epitaxy system. Fundamental aspects concerning the growth and the heterostructures, such as distribution coefficient of Al, critical layer thickness, doping properties, and band discontinuities at the heterojunctions, have been investigated.

Electron traps in dislocation-free In-alloyed liquid encapsulated Czochralski GaAs and their annealing properties

Electron traps in dislocation‐free In‐alloyed liquid encapsulated Czochralski (LEC) GaAs have been studied by deep level transient capacitance spectroscopy. Five traps are observed with activation energies ranging from 0.26 to 0.79 eV below the conduction band. The energies are closely equal to the ones observed in undoped LEC GaAs. However, a notable difference between the In‐alloyed crystal and the undoped crystal exists in effects of annealing on the deep levels. For the In‐alloyed crystal, all levels except EL2(0.79 eV) are unstable under the annealing at 850 °C, while for the undoped crystal, levels EL5(0.41 eV) and EL2 remain stable.

Pressure‐induced Γ‐X crossover in the conduction band of ordered and disordered GaInP alloys

Pressure‐dependent photoluminescence in both ordered and disordered Ga0.5In0.5P is reported. In ordered Ga0.5In0.5P, emissions are observed from both the direct band gap at the Brillouin zone center (Γ) and from the indirect band gap involving the conduction band at the X point of the Brillouin zone. The conduction‐band minima at X and Γ in the ordered phase are found to be lowered in energy by the same amount with respect to those in the disordered phase. Our results support the existence of ordering along the [001] direction in GaInP as proposed recently by Kurtz.

Deep levels in semiconducting In-alloyed bulk n-GaAs and its resistivity conversions by thermal treatments

Thermal conversions of resistivities have been studied for In‐alloyed semiconducting (100–106 Ω cm) n‐GaAs grown by the liquid‐encapsulated Czochralski method. These dislocation‐free as‐grown crystals are converted into semi‐insulating (>107 Ω cm) crystals by annealing at 950  °C for 2 h followed by a fast cooling. Such semi‐insulating crystals can be converted further into crystals with lower resistivities (∼106 Ω cm) by treating them at 470  °C for 100 h. In the analysis of the as‐grown samples by the temperature‐dependent Hall measurements, four levels have been found with activation energies 0.13, 0.20, 0.42, and 0.50 eV. It has been shown that these resistivity conversions are induced by concentration changes of the deep states other than the midgap donor EL2, some of them being the levels found in this study.

Nitrogen doping in AlGaP grown by metalorganic vapor phase epitaxy using ammonia

Doping characteristics of nitrogen in AlGaP grown by metalorganic vapor phase epitaxy have been investigated using ammonia as the nitrogen source. It was found that nitrogen could be successfully incorporated into AlGaP up to as much as 1×1020/cm3 assisted by the gas phase parasitic reaction between trimethylaluminum and ammonia, while nitrogen incorporation into GaP was difficult. Nitrogen incorporation was found to be dependent on several factors such as ammonia concentration, Al composition, V/III ratio, and growth temperature. Exciton recombination bound to isoelectronic nitrogen in AlGaP was observed for the first time by photoluminescence measurement.

Observation of microdefects in indium-doped GaAs crystals by preferential etching and infrared light scattering tomography

Abstract Microdefects in indium-doped GaAs crystals grown by the liquid encapsulated Czochralski (LEC) technique were investigated by using preferential Abrahams-Buiocchi etching (AB etching) and infrared light scattering tomography. Elliptical pits were observed on AB etched (100) surfaces in dislocation-free regions at the front of the ingot, not observed at the tail. The elliptical pits are considered to correspond to microprecipitates. Furthermore, an attempt to improve the homogeneity along the growth direction, the effect of heat treatment on the density of the defects, was investigated.

SOI substrate solutions for recent advanced device applications

SOI substrate technology for recent advanced device applications is reviewed from a standpoint of a dedicated wafer supplier. A structure of Si thin film on sapphire (SOS) has been used for device development and manufacturing from 1970s. Currently a SOI substrate of Si/SiO2/Si structure is widely used for industrial applications.