大功率垂直腔面发射激光器中减小p-DBR串联电阻的途径

Optimization of p-DBR of high power vertical cavity surface emitting laser with low series resistance

为了使垂直腔面发射激光器(VCSEL)实现大功率、高效率的激光输出,对p型分布布喇格反射镜(DBR)形成的同型异质结在界面处存在大势垒导致的高串联电阻和严重发热现象进行了研究。为降低串联电阻,实现VCSEL在室温下的大功率连续发射,分析了p型DBR异质结的势垒结构,对突变异质结的串联电阻进行了计算分析,提出降低势垒高度以及增加扩散浓度是减小串联电阻的主要途径,而漏斗状的掺杂能有效降低体电阻;通过对梯度渐变异质结的分析得出缓变结能有效降低势垒高度;而用Matlab对能带图的数值分析表明,Al0.1Ga0.9As/AlAs接触层中Al组分采取双曲线形式的渐变也能有效降低势垒高度,即降低串联电阻;此外,对于渐变区缓变结的比较表明,采用20～25nm的渐变区宽度即可以得到比较低的势垒高度,同时也不会对DBR的反射率有太大的影响,是较合适的选择。

To obtain the high power and high efficiency laser output for Vertical Cavity Surface Emitting Laser （VCSEL）, the high series resistance and internal heating caused by a big barrier existed in heterojunction from p type Distribution Brrag Reflector（p-DBR） were investigated. In order to reduce the series resistance of p-DBR and realize the continued emitting of a laser, the basic elements and band diagram of the DBR were analyzed in this paper, also the series resistance in the mutation was calculated. On the basis of analysis and calculation, this paper suggests that the main method to reduce series resistance is to decrease the height of barrier and increase the diffusion concentration using funnel-shaped doping. After analyzing the gradient gradual heterojunction, a conclusion shows that the gradually changed heterojunction can reduce the height of the barrier effectively. Numerical analysis of the band diagram by Matlab also indicates that the change in hyperbolic form can reduce the height of the barrier, thereby, the series resistance can be reduced effectively by above methods. Moreover, for the graded region, the wider the band is, the lower the height of the barrier is; for getting a higher reflectivity and a lower barrier, the band width of 20 -25 nm is optimal selection .