Bai, J.
(Department of Electrical and Electronic Engineering, University of Tokushima, 2-1 Minaji-josanjima, Tokushima 770-8506, Japan)
,
Wang, T.
(Satellite Venture Business Laboratory, University of Tokushima, Minaji-josanjima, Tokushima 770-8506, Japan)
,
Izumi, Y.
(Department of Electrical and Electronic Engineering, University of Tokushima, 2-1 Minaji-josanjima, Tokushima 770-8506, Japan)
,
Sakai, S.
(Department of Electrical and Electronic Engineering, University of Tokushima, 2-1 Minaji-josanjima, Tokushima 770-8506, Japan)
AbstractTransmission electron microscope (TEM) and X-ray diffraction (XRD) measurements performed on an InGaN/GaN multiple-quantum-well (MQW) structure deposited on (112̄0) and (0001) sapphire substrates have been investigated. The grown MQW deposited on (112̄0) sapphire substrate are ...
AbstractTransmission electron microscope (TEM) and X-ray diffraction (XRD) measurements performed on an InGaN/GaN multiple-quantum-well (MQW) structure deposited on (112̄0) and (0001) sapphire substrates have been investigated. The grown MQW deposited on (112̄0) sapphire substrate are still oriented along the (0001) direction due to an unusual growth mechanism, which is confirmed by XRD measurement. TEM measurements of the initial stage of the high-temperature GaN growth after the low-temperature buffer GaN layer on (112̄0) sapphire are different from the TEM results obtained for GaN on (0001) sapphire substrate, unlike the XRD patterns which were identical. In addition, a further TEM study indicates that the sample on (112̄0) sapphire substrate shows higher threading dislocation density than that on (0001) sapphire substrate, a fact that is related to the initial stage of the high-temperature GaN layer. Moreover, the sample deposited on (112̄0) sapphire substrate shows a higher density of V-defects incorporating a threading dislocation. The plane-view images of scanning electron microscopy also show that there is a higher density of small dark spots appearing in the paired form compared with that on (0001) sapphire substrate, which generally correspond to screw dislocations. It is generally accepted that V-defects and screw dislocations result in phase separation in InGaN around these defects and finally give rise to a strong exciton-localization effect. This result can explain why an enhanced exciton-localization effect was recently observed in the InGaN/GaN MQW deposited on (112̄0) sapphire substrate.
AbstractTransmission electron microscope (TEM) and X-ray diffraction (XRD) measurements performed on an InGaN/GaN multiple-quantum-well (MQW) structure deposited on (112̄0) and (0001) sapphire substrates have been investigated. The grown MQW deposited on (112̄0) sapphire substrate are still oriented along the (0001) direction due to an unusual growth mechanism, which is confirmed by XRD measurement. TEM measurements of the initial stage of the high-temperature GaN growth after the low-temperature buffer GaN layer on (112̄0) sapphire are different from the TEM results obtained for GaN on (0001) sapphire substrate, unlike the XRD patterns which were identical. In addition, a further TEM study indicates that the sample on (112̄0) sapphire substrate shows higher threading dislocation density than that on (0001) sapphire substrate, a fact that is related to the initial stage of the high-temperature GaN layer. Moreover, the sample deposited on (112̄0) sapphire substrate shows a higher density of V-defects incorporating a threading dislocation. The plane-view images of scanning electron microscopy also show that there is a higher density of small dark spots appearing in the paired form compared with that on (0001) sapphire substrate, which generally correspond to screw dislocations. It is generally accepted that V-defects and screw dislocations result in phase separation in InGaN around these defects and finally give rise to a strong exciton-localization effect. This result can explain why an enhanced exciton-localization effect was recently observed in the InGaN/GaN MQW deposited on (112̄0) sapphire substrate.
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