Visible vertical-cavity surface-emitting laser

摘要

We have designed and fabricated the visible vertical-cavity surface-emitting lasers (VCSEL's) by using metalorganic vapor phase epitaxy. We use the 8$lambda optical cavities with 3 quantum wells in AlGaInP/AlGaAs red VCSEL's to reduce the drift leakage current and enhance the model gain of AlGaInP active region. The structure has a p-type stack with 36 DBR pairs on the top and an n-type with 55-1/2 pairs on the bottom. Using micro-area reflectance spectrum, we try to get a better concordance between the center wavelength of DBR and the emitting wavelength of the active region. We used a component graded layer of 0.05$lambda thick (x $EQ 0.5 approximately 0.9) at the p-type DBR AlGaAs/AlAs interface to reduce the resistance of p-type DBR. We use selective oxidation to define the current injection path. Because the oxidation rate of a thick layer is faster than a thinner one, we grown a thick AlAs layer close to the active region. In this way, we got a smaller active region for efficient confinement of injected carriers (the aperture area is 3 $MUL 3 $mu@m) to reduce the threshold and, at the same time, a bigger conductive area in the DBR layers to reduce the resistance. WE employ Zn doping on the p-side of the junction to improve hole injection and control the Zn dopant diffusion to get proper p-i-n junction. At room temperature, pulse operation of the laser has been achieved with the low threshold current of 0.8 mA; the wavelength is about 670 nm.