Single-ste¥MOVPE growth produces high-speed monolithically integrated photoreceiver
A high-speed monolithically integrated photoreceiver has been fabricated with low-pressure, metal-organic vapor-phase epitaxy (MOVPE) in a single-ste¥growth technique by K. Takahata and colleagues at NTT Opto-electronics Laboratories and NTT System Electronics Laboratories (both Kanagawa-ken, Japan). They incorporated a waveguide PIN photodiode and a high- electron-mobility transistor (HEMT) distributed-baseband amplifier to produce a device that operates at 20 Gbit/s at 1.55 µm. After fabricating the multilayered device, the grou¥used reactive ion etching to produce the 8 ¥ 10-µm waveguide and lithographic patterning to produce the 25 ¥ 0.5-µm gates of the HEMT in the eight-section distributed-baseband amplifier structure.
The frequency response of the monolithically integrated device to a fiber-coupled signal reached the 3-dB cutoff at 20 GHz. The receiver operated at 20 Gbit/s with a well-opened eye pattern and a measured sensitivity of -10.4 dBm at a bit-error rate of 10-9. The external quantum efficiency of the uncoated photodiode was 32%, corresponding to a responsivity of 0.40 A/W; by applying an antireflection coating to the device and optimizing the fiber-to- photodiode coupling, the efficiency should increase to approximately 70%, in turn increasing the sensitivity to -14 dBm. A fully optimized design could potentially achieve a 3-dB cutoff frequency of about 100 GH¥and 100-Gbit/s operation.