VCSEL中布拉格反射体的电流机制和伏安特性

采用张弛法数值求解静电势的泊松方程 ,得出垂直腔面发射激光器 (VCSEL)中 N型和 P型分布布拉格反射体 (DBR)中一个周期单元的精确能带图。并以此为依据 ,从理论上分别分析和比较了多子漂移扩散、纯漂移和热电子发射电流机制所起的作用。指出由一对反对称同型异质结构成的 DBR一个周期单元总是表现出欧姆性 ,但热电子发射电流机制的存在容易使每个结呈现整流特性 ,以致在电流输运过程中起主要作用的是其反向特性 ,导致偏压和电阻过大器件不能正常工作。但是漂移扩散机制具有明显欧姆性 ,在利用缓变 DBR结构消除异质尖峰势垒之后漂移扩散机制将决定主要的电流输运

Current Transport Mechanisms and I-V Characteristics of Bragg Reflectors in VCSEL

Poisson equation of the electrostatic potential has been solved by relaxation method to obtain the accurate band diagrams of a periodic pair of N-and P-type distributed Bragg reflectors(DBR)in vertical-cavity surface-emitting lasers (VCSEL).Accordingly,the I-V characteristics of N and P type DBRs due to three kinds of current mechanisms:the drift-diffusion,pure drift and thermionic emission currents,have been analyzed theoretically.It is shown that,a period of DBR,which consists of a pair of anti-symmetric isotype heterojunctions,always appears to be ohmic,albeit each junction is of rectifying,The I-V characteristics of an anti-symmetric pair will be mainly determined by the reversed characteristics and might result in high voltage drop and high resistance;while the I-V characteristics due to drift-diffusion and /or pure drift current transport will be almost ohmic,and the drift-diffusion will become the final transport mechanisms after using graded DBR to eliminate the spike causing the thermionic emission