The introduction of higher test currents into a VCSEL on wafer, or even a packaged part increases device self-heating, which can degrade the performance characteristics of the device, or worse, damage it. It also increases the potential for burning probe tips during on-wafer testing. This can be problematic, seriously compromising yield. To minimize self-heating, many test specifications require current pulses with pulse widths as short as 10 µs. This requirement in turn drives the need for pulse rise and fall times on the order of 2 µs or less in order to make a fully settled measurement on such a short pulse. While conventional instruments like source measure units (SMUs) are commonly used to test VCSELs, they may not be able to achieve the short current pulse widths needed and will even require manual tuning to ensure the pulse output is usable.
Read our white paper to learn how Keithley Instruments solved this problem to allow faster, simpler testing of VCSEL devices.