title: Indium droplet formation in InGaN thin films with single and double heterojunctions prepared by MOCVD.
abstract: Indium gallium nitride (InGaN) samples with single heterojunction (SH) and double heterojunction (DH) were prepared using metal-organic chemical vapor deposition. SH has a layer of InGaN thin film (thicknesses, 25, 50, 100, and 200 nm) grown on an uGaN film (thickness, 2 μm). The DH samples are distinguished by DH uGaN film (thickness, 120 nm) grown on the InGaN layer. Reciprocal space mapping measurements reveal that the DH samples are fully strained with different thicknesses, whereas the strain in the SH samples are significantly relaxed with the increasing thickness of the InGaN film. Scanning electron microscopy results show that the surface roughness of the sample increases when the sample is relaxed. High-resolution transmission electron microscopy images of the structure of indium droplets in the DH sample indicate that the thickness of the InGaN layer decreases with the density of indium droplets. The formation of these droplets is attributed to the insufficient kinetic energy of indium atom to react with the elements of group V, resulting to aggregation. The gallium atoms in the GaN thin film will not be uniformly replaced by indium atoms; the InGaN thin film has an uneven distribution of indium atoms and the quality of the epitaxial layer is degraded.
authors.affiliation: Graduate Institute of Opto-Mechatronics, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan ; Department of Physics, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 80424, Taiwan ; Advanced Institute of Manufacturing with High-tech Innovations (AIM-HI), National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan.
authors.forename: Yung-Sheng
authors.initials: YS
authors.lastname: Chen
authors.affiliation: Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Che-Hao
authors.initials: CH
authors.lastname: Liao
authors.affiliation: Department of Physics, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 80424, Taiwan.
authors.forename: Chie-Tong
authors.initials: CT
authors.lastname: Kuo
authors.affiliation: Graduate Institute of Opto-Mechatronics, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan ; Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan.
authors.forename: Raymond Chien-Chao
authors.initials: RC
authors.lastname: Tsiang
authors.affiliation: Graduate Institute of Opto-Mechatronics, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan ; Advanced Institute of Manufacturing with High-tech Innovations (AIM-HI), National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan.
authors.forename: Hsiang-Chen
authors.initials: HC
authors.lastname: Wang
keywords: Heterojunction structure; InGaN; Indium droplet; Metal-organic chemical vapor deposition