High-saturation-current charge-compensated InGaAs-InP uni-traveling-carrier photodiode

Charge compensation is utilized in an InGaAs-InP uni-traveling-carrier photodiode to mitigate the space-charge effect. A 20-μm-diameter photodiode achieved a bandwidth of 25 GHz and large-signal 1-dB compression current greater than 90 mA; the output power at 20 GHz was 20 dBm. A smaller /spl sim/100-μm² photodiode exhibited a bandwidth of 50 GHz and large-signal 1-dB compression current greater than 50 mA. The maximum RF output power at 40 GHz was 17 dBm.

For BOTH digital and analog optical transmission systems, photodetectors that operate at high power levels are becoming increasingly important. One approach to achieving high performance in 40-Gb/s optical receivers utilizes optical preamplifiers [1]. However, this results in greatly increased signal levels incident on the photodetector. In the analog domain, high power and high frequency optical links such as cable television, phased array antennas, and photonic analog-to-digital converter systems require photodetectors with high dynamic range, which translates to the capability to operate at high photocurrent levels. Unfortunately, as a result of charge buildup in the photodetector, i.e., space-charge effects and thermal considerations, the speed of a photodetector degrades at high current levels. Various device structures have been reported to reduce the space charge in the depletion region, such as uni-traveling-carrier (UTC) photodiodes [2], a partially depleted absorber photodiode [3], and a velocity-matched distributed photodiode [4].