Fumio Orito

Role of boron in electrical properties of semi‐insulating GaAs grown by the liquid encapsulated Czochralski method

The effects of the predominant residual impurity boron on the electrical properties of In‐doped, dislocation‐free, semi‐insulating GaAs crystals are investigated. Crystals are grown from various arsenic‐rich melts using the vertical magnetic field applied, fully encapsulated Czochralski technique. It is found that carrier and neutral EL2 concentrations in as‐grown crystal and sheet carrier concentration in the Si‐implanted active layer decrease as the boron concentration increases. The effect of boron decreases as the melt composition becomes more arsenic rich. The results suggest that boron decreases the Ga vacancy concentration.

Influence of boron related defects on activation of silicon implanted into undoped semi‐insulating GaAs

The dependence of sheet carrier concentration of a Si‐implanted layer on lattice parameters of undoped liquid encapsulated Czochralski GaAs was investigated. Crystals were grown from near‐stoichiometric melts with varying boron concentrations. Sheet carrier concentration increases with an increase in lattice parameters due to the reduced boron concentration. An anomalous reduction in the lattice parameter suggests that native defects such as BGa VAs are responsible for the increase in the occupancy of implanted Si atoms on As sites.

Anomalous reduction of lattice parameter by residual impurity boron in undoped Czochralski‐grown GaAs

An anomalous reduction of lattice parameter is observed for undoped semi‐insulating liquid encapsulated Czochralski‐grown GaAs by precision lattice parameter measurements with the use of the bond method. The anomalous reduction is though to be due to the incorporation of residual boron from the B2O3 encapsulant. The reduction rate is about 2 times larger than the predicted rate for the boron concentration derived from Vegard’s law. Possible defect models for this phenomenon are discussed.

Total simulation model of high pressure liquid encapsulated Czochralski crystal growth

A numerical model has been made to determine the effect of various geometric and thermal variables. The model consists of the following three blocks: (1) the the entire furnace system in which entire temperature distributions were calculated considering the effects of radiative heat exchange and gas flow; (2) a crystal and melt system in which temperature distributions and the crystal/melt interface were calculated, (3) thermal stress analysis by which resolved shear stress is obtained. Calculated results were in good agreement with experimental results; the temperature response to the change of heater power, the crystal/melt interface shape which was observed from growth striations and etch-pit densities on 4 inch diameter (100) oriented GaAs wafers.

The effect of silicon doping on lattice parameter and silicon related defects in gallium arsenide grown by the gradient freeze method

We investigated the effect of Si doping on the lattice parameter of gallium arsenide single crystals grown by the gradient freeze method. We also studied the carrier concentration and photoluminescence spectra of these crystals. We concluded that the lattice parameters of these crystals depend not only on the silicon concentration, but also on heat treatment and on melt composition. These changes in lattice parameter are assumed to relate to native defects and silicon clusters.

Defect reactions by heat treatment of heavily silicon doped gallium arsenide

Silicon is an amphoteric impurity of gallium arsenide that is present in different defect configurations. This work reports on the effects of heat treatment on defect reactions of heavily silicon‐doped gallium arsenide crystals. The distribution of segregation, lattice parameter, and electrical properties was studied for several heat treatments. When the crystals were bulk‐annealed at between 700 °C and 1000 °C for 20 h, zone‐distributed segregation was observed at the area with a silicon concentration of about 1×1019 cm−3 by etching and x‐ray topography. Regions observed to have silicon‐related segregation exhibited a decrease in lattice parameter when the crystals were annealed below 850 °C for 20 h then quenched. In addition, such regions exhibited little change in lattice parameter when the crystals were annealed above 850 °C. For electrical properties, the largest decrease in carrier concentration and mobility of such regions was observed when the crystals were annealed at 700 °C. This change in the ...

The role of diffusion barrier temperature in gallium arsenide crystals grown by the gradient freeze method

Abstract A gallium arsenide crystal grown by the gradient freeze method is contaminated with silicon and oxygen, from reactions between gallium and quartz. The oxygen concentration increases with the diffusion barrier temperature. This is explained by a thermodynamic analysis of the Ga-As-Si-O system. The effect of reduced oxygen concentration on the electrical properties of GaAs crystals is also discussed.

Formation and behavior of BGaVAs complex defects in gallium arsenide grown by liquid‐encapsulated Czochralski method

The effect of wafer annealing on lattice parameter of liquid‐encapsulated Czochralski (LEC) grown undoped semi‐insulating GaAs crystals is investigated, showing that wafer annealing increases the lattice parameter from an anomalous state below that predicted by Vegard’s law. The sheet‐carrier concentration of a silicon‐implanted layer formed on undoped semi‐insulating GaAs increases with the increase in lattice parameter caused by the wafer annealing. The reduction of BGaVAs complex defects is a reasonable explanation for the increase in lattice parameter and sheet‐carrier concentration. In LEC‐grown silicon‐doped GaAs crystals, no anomalous reduction of lattice parameter is observed in as‐grown crystals. It is speculated that the silicon introduced into the crystal from the melt fills the VAs vacancies in the GaAs crystal before BGaVAs forms. BGaVAs complex defects in undoped GaAs crystal must be formed during the post‐growth cooling process.

Growth of Cr doped GaAs single crystals by the gradient freeze method

Chromium doped GaAs single crystals are grown by a new technique, in which the growth rate is initially high and lowered automatically by a preprogrammed furnace cooling rate in the conventional gradient freeze method. It is shown that Si and Cr distribution in Cr doped GaAs single crystals along the growth direction depends on crystal growth rate. The effect of growth rate on resistivity and leakage current distribution of Cr doped GaAs single crystals is also reported. Distribution of deep levels in the crystal grown by the new technique and the relation to impurity distribution are investigated by photoluminescence spectroscopy.

Effects of semi-insulating gallium arsenide substrate properties on silicon implanted active layer

Effects of carbon, boron, and EL2 concentrations in undoped semi-insulating GaAs crystal on silicon-implanted active layers are quantitatively examined. The mechanisms for these effects are investigated. Reducing carbon and boron concentrations, growing crystal from a near-stoichiometric melt, and boule annealing all improve the uniformity in silicon-implanted active layers formed on undoped semi-insulating GaAs substrates. Seed-to-tail uniformity within boule and boule-to-boule uniformity are also improved. These undoped semi-insulating GaAs substrates are promising for IC applications. The reliable supply of GaAs substrates is moving high-performance GaAs devices into manufacturing.<<ETX>>