EFFECT OF CARRIER DIFFUSION IN OXIDIZED VERTICAL-CAVITY SURFACE-EMITTING LASERS DETERMINED FROM LATERAL SPONTANEOUS EMISSION

The effect of carrier diffusion on threshold current is studied quantitatively for the oxide-aperturbed 780 nm vertical-cavity surface-emitting lasers (VCSEL) from the measured spontaneous emission. The oxide aperture size of 2–10 μm is prepared and characterized. The diffusion coefficient of 4.6 cm2/s and the nonradiative recombination coefficient of 6.8×107/s are obtained using the independence of the nonradiative recombination coefficient on the laser aperture size. The contribution of carrier diffusion loss is 42% of the threshold current for the 2 μm VCSEL. The relative contribution of the diffusion becomes smaller for the larger devices as is expected.