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Kim Y.H.,Korea Research Institute of Standards and Science | Kim C.S.,Korea Research Institute of Standards and Science | Noh Y.K.,Wooree LST Corporation | Noh Y.K.,Chungnam National University | And 2 more authors.
Journal of Crystal Growth | Year: 2011

The microstructural properties of AlN layers grown on a Si(1 1 1) substrate were studied in detail using transmission electron microscope techniques to determine phase transition behaviors. AlN layers were grown in the wurtzite (WZ) and zinc-blende (ZB) polytypes. The dominant phase of AlN was transformed from a ZB structure to a WZ structure as the substrate temperature increased. Many protrusions were observed on the surfaces of AlN layers, and their density was decreased with an increase in the substrate temperature; these protrusions originated from the WZ structure of AlN and not the ZB structure. In our experiment, WZ-AlN grains were frequently observed at the edge and/or on the surface of the ZB-AlN grains at relatively low substrate temperatures. The preferred crystallographic orientation relationships of the {111} ZB-AlN||{111}Si and <110> ZB-AlN||<110>Si between the ZB-AlN and the Si substrate and the (0001)WZAlN||(111)Si and [1210] WZ-AlN//[11()0]Si between WZ-AlN and the Si substrate were identified in our experiment. © 2011 Elsevier B.V. All rights reserved.


Park S.-H.,Catholic University of Daegu | Ahn D.,University of Seoul | Koo B.-H.,Wooree LST Corporation
Semiconductor Science and Technology | Year: 2010

Optical gain characteristics of a-plane CdZnO/MgZnO QW structures with a (1 1 0) crystal orientation were theoretically investigated by using the non-Markovian gain model with many-body effects. These results are compared with those of c-plane quantum-well (QW) structures with a (0 0 0 1) crystal orientation. In the case of the c-plane, the optical gain gradually decreases with increasing Cd composition. This is mainly due to the increase in the piezoelectric and spontaneous polarizations. On the other hand, in the case of the a-plane, the optical gain gradually increases with increasing Cd composition. This can be explained by the fact that the quasi-Fermi-level separation increases with the Cd composition. The a-plane shows much larger optical gain than the c-plane, in particular, for QW structures with a larger Cd composition. This means that the crystal orientation effect is much dominant for the QW structure with a large Cd composition. Also, in the case of a low Cd composition, it is found that the CdZnO/MgZnO QW structure shows much larger optical gain than that of the a-plane InGaN/AlGaN QW structure. © 2010 IOP Publishing Ltd.


Kim Y.H.,Korea Research Institute of Standards and Science | Ruh H.,Korea Research Institute of Standards and Science | Noh Y.K.,Wooree LST Corporation | Noh Y.K.,Chungnam National University | And 2 more authors.
Journal of Applied Physics | Year: 2010

The microstructural properties of a GaN layer grown on a patterned sapphire substrate (PSS) were studied in detail using transmission electron microscope techniques to determine dislocation and growth behaviors. Regular and uniform recrystallized GaN islands were observed on the protruding pattern. On a flat sapphire surface, the crystallographic orientation relationship of 〈 1- 2 1- 0 〉GaN on FS // 〈 1100 〉 sapphire and { 1101 }GaN on FS // { 1213 } sapphire existed between the GaN and the substrate. On the other hand, the orientation relationship of 〈 1210 〉 GaN layer // 〈 1210 〉 GaN island on IS // 〈 1100 〉sapphire and { 1101 } GaN layer // { 0002 }GaN island on IS // { 1213 } sapphire was confirmed among the GaN layer, the recrystallized GaN islands on an inclined sapphire surface and the PSS. The flat surface among the protruding patterns began to fill rapidly with GaN. Then, the GaN gradually overgrew the protruding pattern and coalesced near the summit as the growth time increased. The generation of threading dislocations was observed in the vicinity of the coalescence points near the top of the protruding patterns. © 2010 American Institute of Physics.


Noh Y.K.,Chungnam National University | Kim M.D.,Wooree LST Corporation | Oh J.E.,Hanyang University | Yang W.C.,Dongguk University
Journal of the Korean Physical Society | Year: 2010

We have investigated the structural and the optical properties of GaSb films with a thin AlSb buffer layer and a GaSb interlayer grown on Si (100) substrates by using molecular beam epitaxy. Reflection high-energy electron diffraction and atomic force microscopy measurements of the thin AlSb buffer layers showed that the surface had uniformly-sized quantum dots with a low defect density. The surface roughness of a GaSb film with a thin GaSb interlayer grown at a low temperature was decreased by a factor of about 5 compared with the roughness of the GaSb film without the thin GaSb interlayer. In addition, double-crystal X-ray diffraction and photoluminescence results showed that the structural and the optical properties of the GaSb layer with the GaSb interlayer were improved significantly. We suggest that the significant reduction of the dislocation density in the GaSb film was due to the dislocations being prevented from propagating into the GaSb overlayer by the thin GaSb interlayer.


Patent
Wooree Lst Co. | Date: 2010-10-01

There is provided a compound semiconductor light emitting device capable of optimizing strain applied to an active layer and a clad layer to minimize a piezoelectric field and spontaneous polarization in an active layer and to maximize light emission efficiency. In a compound semiconductor light emitting device having a structure in which a buffer layer, a first clad layer, an active layer, and a second clad layer are sequentially deposited, a strain induction layer and a strain control layer intersect at least once and are deposited between the buffer layer and the first clad layer, the strain induction layer performs induction so that compressive strain to be applied to the active layer is dispersed to the strain control layer, and the compressive strain applied to the active layer is reduced as the compressive strain is applied to the strain control layer.

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