Han-Din Liu

Ultraviolet Single Photon Detection With Geiger-Mode 4H-SiC Avalanche Photodiodes

We report 4H-SiC avalanche photodiodes operated in Geiger mode for single photon detection at 265 nm. At room temperature, the single photon detection efficiency is 14% with a dark count probability of 1.7 x 10-4. Since the external quantum efficiency is 21% at 265 nm, it follows that 65% of the absorbed photons are counted as avalanche events. The jitter of the photodiodes is also characterized.

High Detection Sensitivity of Ultraviolet 4H-SiC Avalanche Photodiodes

We report 4H-SiC p-i-n avalanche photodiodes (APDs) with very low dark current. When biased for a photocurrent gain M of 1000, a 100-mum-diameter device exhibits dark current of 5 pA (63 nA/cm2), corresponding to primary multiplied dark current of 5 fA (63 pA/cm2). The peak responsivity at unity gain is 93 mA/W (external quantum efficiency = 41%) at lambda = 280 nm. The excess noise factor corresponds to k = 0.1. Detection of several tens of femtowatts of ultraviolet light is reported.

Thermal Analysis of High-Power InGaAs–InP Photodiodes

InGaAs-InP charge-compensated unitraveling-carrier photodiodes with thick depletion region are demonstrated. A 40-mum-diameter photodiode achieved 10-GHz bandwidth and 24.5dBm RF output power. A 100-mum-diameter photodiode achieved bandwidth of 2 GHz and 29 dBm RF output power. Simulation of the temperature distribution in devices is also presented

High-Detectivity and High-Single-Photon-Detection-Efficiency 4H-SiC Avalanche Photodiodes

We report large-area, 250-mum-diameter, 4H-SiC avalanche photodiodes with low dark current and high gain. At room temperature, the dark current density is 59.5 nA/cm2 at a gain of 1000. An external quantum efficiency of 48% at 280 nm is achieved at unity gain with a recessed-window structure. The differential resistance of the recessed-window device at zero bias is estimated to be 6times1014 Omega. As a result of high external quantum efficiency, large area, and large differential resistance, a record high specific detectivity of 4.1times1014 cmHz1/2 W-1, has been achieved. In Geiger mode operation, high single photon detection efficiency of 30% with dark count probability of 8times10-4 is reported.

Epitaxially-grown Ge/Si avalanche photodiodes for 1.3µm light detection

We designed and fabricated Ge/Si avalanche photodiodes grown on silicon substrates. The mesa-type photodiodes exhibit a responsivity at 1310nm of 0.54A/W, a breakdown voltage thermal coefficient of 0.05%/°C, a 3dBbandwidth of 10GHz. The gain-bandwidth product was measured as 153GHz. The effective k value extracted from the excess noise factor was 0.1.

4H-SiC PIN Recessed-Window Avalanche Photodiode With High Quantum Efficiency

We report a 4H-SiC PIN recessed-window avalanche photodiode with a peak responsitivity of 136 mA/W (external quantum efficiency = 60%) at lambda = 262 nm, corresponding to more than a 50% increase in external quantum efficiency compared to nonrecessed structures. The dark current was 90 pA at a photocurrent gain of 1000. Avalanche gains of over 106, k ~ 0.1, and a spatially uniform response were achieved.

Geiger-Mode Operation of Ge-on-Si Avalanche Photodiodes

Single-photon detection is reported for Ge-on-Si separate-absorption-charge-multiplication avalanche photodiodes. Single-photon detection efficiency of 14%, dark count rate of 108 s-1, and timing resolution of 117 ps were achieved.

Demonstration of Ultraviolet 6H-SiC PIN Avalanche Photodiodes

We report electrical and electrooptical characteristic of mesa-structure 6H-SiC PIN avalanche photodiodes. At a gain of 1000, the dark current density is 9.2 muA/cm2. The excess noise factor corresponds to a k value of ~0.1. In addition, peak responsivity of 80 mA/W was observed at 290 nm (external quantum efficiency of ~35%)

A self-assembled microbonded germanium/silicon heterojunction photodiode for 25 Gb/s high-speed optical interconnects

A novel technique using surface tension to locally bond germanium (Ge) on silicon (Si) is presented for fabricating high performance Ge/Si photodiodes. Surface tension is a cohesive force among liquid molecules that tends to bring contiguous objects in contact to maintain a minimum surface energy. We take advantage of this phenomenon to fabricate a heterojunction optoelectronic device where the lattice constants of joined semiconductors are different. A high-speed Ge/Si heterojunction waveguide photodiode is presented by microbonding a beam-shaped Ge, first grown by rapid-melt-growth (RMG) method, on top of a Si waveguide via surface tension. Excellent device performances such as an operating bandwidth of 17 GHz and a responsivity of 0.66 and 0.70 A/W at the reverse bias of −4 and −6 V, respectively, are demonstrated. This technique can be simply implemented via modern complementary metal-oxide-semiconductor (CMOS) fabrication technologies for integrating Ge on Si devices.

Proton-Implantation-Isolated Separate Absorption Charge and Multiplication 4H-SiC Avalanche Photodiodes

We report reach-through structure 4H-SiC avalanche photodiodes isolated by proton implantation. These devices achieved low dark current (85 pA at a gain of 1000) and high external quantum efficiency ( 75% at 260 nm).