Numerical Analysis of Difficulties of Growing Large-Size Bulk β-Ga2O3 Single Crystals with the Czochralski Method

Xia Tang,Bing Gao,Yue Yu,Sheng Liu,Botao Liu

doi:10.3390/cryst11010025

Abstract

The difficulties in growing large-size bulk β-Ga2O3 single crystals with the Czochralski method were numerically analyzed. The flow and temperature fields for crystals that were four and six inches in diameter were studied. When the crystal diameter is large and the crucible space becomes small, the flow field near the crystal edge becomes poorly controlled, which results in an unreasonable temperature field, which makes the interface velocity very sensitive to the phase boundary shape. The effect of seed rotation with increasing crystal diameter was also studied. With the increase in crystal diameter, the effect of seed rotation causes more uneven temperature distribution. The difficulty of growing large-size bulk β-Ga2O3 single crystals with the Czochralski method is caused by spiral growth. By using dynamic mesh technology to update the crystal growth interface, the calculation results show that the solid–liquid interface of the four-inch crystal is slightly convex and the center is slightly concave. With the increase of crystal growth time, the symmetry of cylindrical crystal will be broken, which will lead to spiral growth. The numerical results of the six-inch crystal show that the whole solid–liquid interface is concave and unstable, which is not conducive to crystal growth.

Highlights

Gallium oxide has five polymorphisms, and other phases transform into the β phase at high temperature. β-Ga2 O3 is the most stable crystal structure, with a melting point of 1800 ◦ C under atmospheric pressure [1,2]
Gallium oxide has a wider band gap than SiC and GaN, and its unique properties make it so that it is used in many devices, including Schottky barrier diodes (SBDs), inverters, equipment, or circuits used in high-temperature, high-humidity, and high-radiation environments, and field-effect transistors (FET) [5]
More vortices in the flow field could affect the quality of the phase boundary and lead to spiral growth

Summary

Introduction

Gallium oxide has five polymorphisms, and other phases transform into the β phase at high temperature. β-Ga2 O3 is the most stable crystal structure, with a melting point of 1800 ◦ C under atmospheric pressure [1,2]. Gallium oxide has a high electrical breakdown field and is an ideal material for the manufacture of high-power diodes. Gallium oxide can be used to manufacture various light-emitting diodes (LEDs) and laser diodes (LDs), new fluorescent materials, and gas sensors based on β-Ga2 O3 , as well as solar-blind UV detectors and high-temperature, high-frequency, and high-power electronics [3]. Gallium oxide has a wider band gap than SiC and GaN, and its unique properties make it so that it is used in many devices, including Schottky barrier diodes (SBDs), inverters, equipment, or circuits used in high-temperature, high-humidity, and high-radiation environments, and field-effect transistors (FET) [5]. One way to reduce cost is to increase the crystal diameter. The crystal diameter enlargement is quite difficult.

Methods

Results

Conclusion