| Research Abstract |
Although high yield growth technology of group III nitrides on sapphire using low temperature deposited buffer layer which had been established by us in 1986 brought about the bright blue and green light emitting diodes and violet laser diodes, it still has the problem of high density threading dislocations.
In order to reduce threading dislocations in the group III nitride films, we intentionally applied horizontal biaxial stress during growth, thereby bend the threading dislocations. Intentional stress was applied by forming trench structure, by which growth plane was inclined from the c-axis direction. Self induced stress field around dislocations causes inductive force along growth plane, thereby almost all types of dislocations including pure-screw, pure-edge, and mixed type dislocations are bent. This mechanism can be applied not only in case of GaN but also applicable to AlGaN.Low dislocation density AlGaN has been achieved for the first time.
In this study, we also established the in-situ stress monitoring system, by which we can precisely determined the critical thickness for crack formation. We also found the impurity hardening effect in nitrides for the first time.
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