ABSTRACT
Sung-Nam Lee3’ b, J K Son3, H S Paeka, T Sakonga, J S Kwaka, K H Ha, O H Nam3, and Y Park3 aPhotonics Lab, Samsung Advanced Institute of Technology, Suwon 440600, Korea Euijoon Yoonb bSchool of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea J Y Kimc, and Y -H Choc, departm ent of Physics and Institute for Basic Science Research, Chungbuk National University, Cheongju 361-763, Korea S S Kimd, Y J Leed, and D Y Nohd Department of Materials Science and Engineering, K-JIST, Gwangju
500-712, Korea
Abstract. To investigate the influence of thermal damage on InGaN MQWs, the MQW sample was heated to the high temperature and cooled down and its structural and optical properties were compared with the MQW sample cooled down without high temperature thermal treatment. The surface morphology of InGaN MQWs changes from a spiral to a step structure after the high temperature treatment, which is induced by the desorption and the surface migration of In and Ga adatoms during the high temperature treatment. In HRXRD (0004) co /2 0 scan, the intensity fringes between high order satellite peaks disappear, which suggests that the interface quality of InGaN MQWs be also deteriorated by high temperature treatment. Temperature dependence of PL measurement shows that InGaN MQWs without high temperature thermal treatment had higher internal quantum efficiency and the lower localization effect. 1
1. Introduction Recently, epitaxial growth of Ill-nitrides has been focused on the improvement of optical and crystal qualities of InGaN multi-quantum wells (MQWs) since they are used as active layers of GaN-based optoelectronic devices such as blue/green light emitting diodes (LEDs) and violet/blue laser diodes (LDs) [1-3]. However, the growth of high quality InGaN layer by metalorganic chemical deposition (MOCVD) has been a challenging issue due to extensive decomposition of InN at temperature above 500 °C and low cracking efficiency of ammonia below 1000 °C [1]. In general, InGaN layers are commonly grown at much lower temperature compared with the growth temperatures
used in GaN films to optimize the incorporation of indium in the InGaN layer [1]. On the other hand, the growth temperature above 1000 °C should be required to get a high quality p-type GaN layer. Therefore, in the film growth of LEDs and LDs, the high temperature ramp-up step above 1000 °C is added to grow the p-type GaN layer after the growth of InGaN active layer below 800 °C [2]. Due to the significant difference in the growth temperature, it is believed that the InGaN active layer may be damaged by high temperature ramp-up step. Some research groups have reported the thermal stability of InGaN layers by studying the thermal annealing effects on InGaN film [3] the effect of ammonia flow during high temperature ramp-up step after the growth of InGaN MQWs [4], and the thermal decomposition of InGaN/GaN MQWs [5]. Nonetheless, there have been few systematic reports regarding the effect of thermal damage on the surface morphological, optical, and structural characteristics of the InGaN/InGaN MQWs by high temperature ramp-up process. In this work, we systematically investigated the influence of thermal damage on InGaN MQWs.
