In situ thickness monitoring and adjusting during MBE growth for 980 nm VCSEL

Since a typical VCSEL structure contains large numbers of layers and requires a long growth duration, the precisely controllable growth by MBE on large-area substrates is difficult. Several in situ thickness monitoring techniques have been used. We study the apparent substrate temperature oscillation of GaAs, AlAs and GaAs/AlAs DBR by an infrared thermometer. Based on a quasi-blackbody emission model, the refractive indices of GaAs and AlAs at high temperature are obtained by simulation analysis. The effects of refractive index n and extinction coefficient /spl kappa/ on the oscillation curve are studied, respectively. Then the whole growth of VCSEL is monitored, the accurate growth rate measured and mode wavelength adjusted during the growth. The VCSEL structure contains 23.5 pairs of AlAs/GaAs n-type DBR, 20.5 pairs of AlAs/Ga/sub 0.7/Al/sub 0.3/As/GaAs step p-type DBR, a strained In/sub 0.2/Ga/sub 0.8/As/GaAs 3QW active region and GaAs space layer.