高In組成之InGaN量子結構光電物理行為之研究

Abstract

最近的一年來，我們在GaN及InGaN薄膜低溫成長技術已取得重要突破，我們不僅完成了低溫高光學品質的GaN薄膜製備，亦成為全世界第一個MOCVD研究群能夠成長全波段InGaN三元化合物的團隊。這主要可歸因於我們自組一種雙加熱系統的MOCVD，可以分別提供氮化物所需之成長溫度及NH3分解所需的裂解溫度。在本計劃中我們擬庚續原先GaN及InGaN的研究，並特別強調量子井及量子點光學及電學之特性探討，其詳細內容茲分述如下： (1) 建立GaN及InGaN薄膜低溫磊晶最佳化之磊晶條件，並利用PL、PLE、吸收光譜及深層能階暫態能譜量測，找出深階能階之能階位置及缺陷密度，並藉以調整磊晶參數以獲得最佳的成長條件。 (2) 提升p-GaN及p-InGaN薄膜的活化效率，在本計畫擬利用低背景濃度的GaN及InGaN薄膜藉由降低補償效應及活化能之方法提升p-GaN及p-InGaN薄膜的電洞濃度。 (3) 製備綠光及紅光氮化銦鎵/氮化鎵量子井，擬利用前述所發展之最佳化條件所成長高品質的低溫InGaN緩衝層及低溫GaN能障層，提升InGaN量子井之發光效率。 (4) 製備高品質綠、紅光的氮化銦鎵量子點結構，擬利用變溫及變能量時間解析光譜分析在量子點之能階中電子躍遷能階、躍遷速率以及載子動力行為。

In last year, we have accomplished a major breakthrough in low-temperature GaN and InGaN growth technique. By utilizing a novel two heating systems in our home-made MOCVD reactor, we are able to reduce GaN growth temperature down to as low as 700oC with optical quality comparable to that high temperature GaN film. Regarding InGaN growth, more amazing results are attained. We have realized full-spectrum light emissions of entire composition of InGaN film growth. To our knowledge, such achievements have never been reported by other MOCVD group. In this project, we plan to continue our previous research with emphasis on the studies of optical and electrical properties of InGaN quantum well and quantum dot physical structures. The details are listed as follows: (1) Adjusting growth parameters including growth temperature, V/III ratio, input group gas ratio, in partucluar upper graphite temperature, which is employed to enhance NH3 cracking efficiency, to optimize the growth conditions for GaN and InGaN, repectively, in accord with the results of the following measurements, such as PL, PL excitation, absorption, and DLTS spectroscopy. (2) Imporving activation efficiencies of p-type GaN and InGaN films by means of use of low background high quality, low-temperature GaN and InGaN films grown by our home-made MOCVD reactor primarily via reduction of compensation effects as well as activation energy. (3) Studying the optical properties of InGaN/GaN quantum well structures prepared by our newly developed low-temperature growth technique with focuses on the effects of low-temperature grown GaN barrier and InGaN buffer layer to light emission quantum efficiency. (4) Extending our studies on InGaN quantum dot structures with light emission at either green or red light by employing temperature dependent and energy dependent TRPL measurements to explore electron transition energy, transition rate and carrier dynamic behavior inbetween quantization energy state of QD structure.