Shin-ichi Akai

LEC growth of Te-doped GaSb single crystals with uniform carrier concentration distribution

Abstract Large diameter (35–50 mm) Te-doped 〈100〉 GaSb single crystals have been successfully grown from a non-stoichiometric melt by the liquid encapsulated Czochralski (LEC) method. The X-ray transmission topograph shows that the 〈100〉 crystals have extremely low dislocation densities (less than 1 cm −2 ), weak striations and no facets. Hall measurements show that the carrier concentration (7.1×10 18 cm −3 ) distribution is within ±5% deviation over (100) wafers.

Low dislocation density Si-doped GaAs single crystal grown by the vapor-pressure-controlled Czochralski method

Si-doped GaAs substrates have been widely used for optical devices. Recently, as the device fabrication process has changed, larger diameter substrates can be used. Almost dislocation-free Si-doped GaAs crystals of 75 mm diameter, which are suitable for the fabrication of optical devices, have been successfully grown using our vapor-pressure-controlled Czochralski (VCZ) method. The generation of slip dislocations could be suppressed and the growth of the dislocation-free crystal was achieved by decreasing the thickness of B2O3. The VCZ crystals contained a large amount of unintentionally doped boron (B) of about 1018 cm−3. By comparing the electrical data of the VCZ crystals with those of the gradient freeze (GF) crystal free from B, it is found that B acceptors decrease the intrinsic compensation ratio ([SiAs][SiGa]).

Effects of Whole Ingot Annealing on 1.49 eV PL Properties in LEC-Grown Semi-Insulating GaAs

The effects of whole ingot annealing on 1.49 eV photoluminescence (PL) properties at 4.2 K in undoped/low-Cr doped LEC-grown semi-insulating GaAs have been studied. It has been found that whole ingot annealing considerably increases the PL intensities with no significant degradation of semi-insulating properties. It has been also found that whole ingot annealing drastically reduces both the radial variation of PL intensity distribution and the difference of PL intensities between seed end and tail end.

1 – Bulk Crystal Growth

This chapter reviews several important issues in III–V compound crystal growth. It focuses on GaAs and InP and recent advancements in their crystal growth technology. As the crystal size increases, it is difficult to reduce the dislocation density. In order to overcome it, a low temperature gradient growth under an ambient of group V element is necessary. In addition, a control of solid–liquid interface shape is also essential. The basic objectives in the development of crystal growth technology are larger crystals, reduction of crystal defects, and higher purity. Horizontal bridgman (HB) and liquid encapsulated czochralski (LEC) are two representative growth methods of III–V compound crystals. The HB method is favorable for reducing the dislocation density and is, therefore, used in providing substrates for optical devices. The LEC method is advantageous for increasing the crystal diameter and is therefore used in providing substrates for electronic devices. The most important subject to be grappled by a material supplier is to increase the reproducibility of carbon content from wafer-to-wafer or lot-to-lot. In order to increase the integration density of GaAs ICs, the influence of a dislocation on the device performance needs to be clarified. In addition, stoichiometry control is important in the case of compound crystals.