CdTe:Li晶体中ALi°受主与电子及激子的相互作用

用两种不同方法实现了在CdTe晶体中Li杂质的低温扩散。其中后一种无Te预扩散的方法是首次报导的。为研究在CdTe:Li中ALi°受主与电子和激子的相互作用,分析了各种发光机制中的动力学过程,观测了(e,ALi°)及(ALi°,X)发光的激发光强度效应。(ALi°、X)束缚激子可以热离解成一个自由电子和一个自由空穴而留下一个中性受主ALi°,其束缚能为Eb=4meV。在不同强度的光激发下,研究了(e,ALi°)辐射复合中电子—声子耦合。当杂质中心不变时,平均声子数N～0.1基本上保持不变,它是杂质中心波函数半径的一个量度。若假定杂质中心上电荷分布为Gaussian形,计算出表征电荷在杂质中心局域程度的常数α～160Å。

INTERACTION OF ALi° WITH ELECTRONS AND EXCITONS IN CdTe:Li

By two ways the impurity Li was diffused into CaTe crystals. The anneal of sample a was made in a quartz tube at 350℃, under Te atmosphere for 320 hours. Li diffusion was made from Li2CO3 solutions deposited on the polished wafer surface in a horizontal furnace, under a continuous flow of H2-N2 mixture. The temperature was 350℃, and the diffusion time was one hour. Li diffusion of the samples b and c was similar to that of sample a but without the first stage. The temperature was 450℃, and diffusion time one hour and 0.5 hour respectively. The second way without prediffusing of Te is reported first time.In order to investigate the interaction of ALi° with electrons and excitons in CdTe:Li, the dynamic processes of various luminescence mechanism were analysed. The effect of excitation intensities of (e, ALi°) and (ALi°, X) emission were observed at UK. And two relationships, Ilum-Iexc and Ilum-Iexc1.5 were obtained respectively. A bound exciton (ALi°, X) could be dissociated thermally into an electron and a hole leaving a neutral acceptor ALi°,(ALi°,X)→ALi°+e+h. By fitting the curve to the experimental data of the integral intensities in (ALi°, X) emissions, we got that the bound energy of exciton was about 4meV.The electron-phonon coupling for various Iexc in (e, ALi°) was analysed. When the trapped centres are the same, N, the mean number ofemitted phonons is a constant. And N is a measure of the radius of the trapped carrier wave function if the charge distribution of trapped carriers can be approximated by a Gaussion function. The constant a characterizing the localization of the carrier at a centre is about 160Å.