应变AlN表面生长动力学  

Growth Mechanism of Strained AlN Surfaces

作　　者：曹志峰[1] 林伟[2] 庄芹芹[3] 李书平[2] 康俊勇[2] 

机构地区：[1]福建医科大学数理与计算机教学部基础医学院,福建福州350108 [2]厦门大学物理与机电工程学院福建省半导体材料及应用重点实验室,福建厦门361005 [3]厦门理工学院光电与通信工程学院,福建厦门361024

出　　处：《厦门大学学报（自然科学版）》2015年第3期378-383,共6页Journal of Xiamen University：Natural Science

基　　金：国家重点基础研究发展计划(973计划)(2012CB619300);国家高技术研究发展计划(863计划)(2014AA032608);国家自然科学基金(11404271);福建省教育厅科技项目B类(JB13150)

摘　　要：AlN半导体通常在异质衬底上外延,生长过程中往往承受较大的晶格失配应力.基于第一性原理,研究了应变AlN表面生长基元,如Al和N原子以及Al-Nn团簇的微观生长动力学.与非应变AlN比较显示,N原子形成焓有所提升,难以形成稳定吸附;而Al原子则由活跃转为稳定吸附.通过比较不同团簇表明,Al-N3团簇结合能远低于Al-N、AlN2和Al-N4团簇,最为稳定.进一步计算不同生长氛围下形成焓差异的结果显示,应变Al-N3团簇形成焓略有提升,但总体仍呈现稳定吸附的特性.基于各生长基元在不同生长氛围下应变AlN的动力学特性差异,设计了分层生长步骤.生长初期通过生长源的切换,分别提供有利于N原子和Al原子扩散的氛围,以形成均匀分布的晶核;再通过同时供给N和Al源形成Al-N3团簇,利用其跨度大、吸附稳定等特性,促进表层晶核间的跨越生长,以形成连续的二维外延层,为在大失配异质衬底上外延致密、平整、优质的AlN薄膜提供了新的方案.AlN,emerging as a promising semiconductor compound for ultraviolet optoelectronics is commonly heteroexpitaxially grown on sapphire suffering from large lattice mismatch.In this work,we study the growth mechanism of the growth units including Al,N,Al-N and Al-N cluster on strained AlN surface based on first principle simulations.Compared with unstrained AlN,the formation entropy（FE）of N atoms is increased,which is hard to stably absorb on the surface,while active Al atoms turn to be stable on the surface.By evaluating the binding energy,the energy value of Al-N3 cluster is found to be lower than that of Al-N,Al-N2 and AlN4,indicative of the most likely cluster structure among clusters as the growth unit.The calculation of the FE of Al-N3 shows that Al-N3 cluster turns to be the most stable growth units although its FE is slightly increased under different growth conditions.On account of the growth mechanism,we design hierarchical growth steps.At the initial stage,the favorable atmosphere is provided for N and Al atoms,respectively,in order to form a uniform nucleation.The simultaneous supply of N and Al sources yields Al-N3 cluster with large span and stable absorption,which facilitates the growth across the nucleuses so as to continuous 2Depilayer.Our present design gives a general theoretical background and a new guideline to stimulate experimental fabrication of AlGaN films with compact structure,atomic smoothness,and high quality.

关 键 词：高Al组分AlGaN 第一性原理 表面生长 

分 类 号：O472[理学—半导体物理]