Behaviors of AlGaN Strain Relaxation on a GaN Porous Structure Studied with d-Spacing Crystal Lattice Analysis
Hao-Yu Hsieh,
Ping-Wei Liou,
Shaobo Yang,
Wei-Cheng Chen,
Li-Ping Liang,
Yueh-Chi Lee,
Chih-Chung (C. C.) Yang
Affiliations
Hao-Yu Hsieh
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Ping-Wei Liou
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Shaobo Yang
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Wei-Cheng Chen
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Li-Ping Liang
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Yueh-Chi Lee
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Chih-Chung (C. C.) Yang
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
The high porosity of a GaN porous structure (PS) makes it mechanically semi-flexible and can shield against the stress from the thick growth template on an overgrown layer to control the lattice structure or composition within the overgrown layer. To understand this stress shield effect, we investigated the lattice constant variations among different growth layers in various samples of overgrown Al0.3Ga0.7N on GaN templates under different strain-relaxation conditions based on d-spacing crystal lattice analysis. The fabrication of a strain-damping PS in a GaN template shields against the stress from the thick GaN template on the GaN interlayer, which lies between the PS and the overgrown AlGaN layer, such that the stress counteraction of the AlGaN layer against the GaN interlayer can reduce the tensile strain in AlGaN and increase its critical thickness. If the GaN interlayer is thin, such that a strong AlGaN counteraction occurs, the increased critical thickness can become larger than the overgrown AlGaN thickness. In this situation, crack-free, thick AlGaN overgrowth is feasible.
