Single crystal zinc oxide is a wide band gap semiconductor with great potential for a variety of commercial applications including substrates, UV photodetectors, acoustic wave devices, light emitting diodes, laser diodes, and high frequency electronic devices. ZnO is unique in that it has a very high exciton binding energy (60 meV) enabling stability at higher device operating temperatures, and it is highly resistant to radiation damage compared even to GaN. Bulk growth of ZnO single crystals is being conducted using the following primary methods: hydrothermal solution growth, seeded sublimation growth, and pressurized melt growth. Cermet, Inc. has employed the pressurized melt growth approach with much success. ZnO dissociates upon heating into a defective ZnO1−x structure, which is addressed by providing an overpressure of oxygen in the growth environment. Single crystals nucleate and grow from the stoichiometric ZnO melt, which is contained in a thin layer of cooled, polycrystalline ZnO, eliminating crucible-introduced impurities. From these large ingots, high quality (~104 defects cm−2, linewidths as low as 49 arcsec), high purity ZnO crystals have been crystallized, oriented, and shaped into round or square boules and eventually processed into epitaxial-ready substrates. The pressurized melt growth approach is highly scalable and can accommodate high growth rates (up to 1 cm h−1), which are two criteria that are appealing to industrial productioin of high quality substrates.
[1]
D. C. Reynolds,et al.
Similarities in the bandedge and deep-centre photoluminescence mechanisms of ZnO and GaN
,
1997
.
[2]
W. Zulehner.
Historical overview of silicon crystal pulling development
,
2000
.
[3]
G. Foti.
Silicon carbide: from amorphous to crystalline material
,
2001
.
[4]
David C. Look,et al.
Recent Advances in ZnO Materials and Devices
,
2001
.
[5]
Hideo Iwasaki,et al.
Historical review of quartz crystal growth
,
2002
.
[6]
P. Rudolph,et al.
Bulk growth of GaAs : An overview
,
1999
.