Hyo-Soon Kang

Si avalanche photodetectors fabricated in standard complementary metal-oxide-semiconductor process

The authors report silicon avalanche photodetectors (APDs) fabricated with 0.18μm standard complementary metal-oxide-semiconductor (CMOS) process without any process modification or a special substrate. When the bias is above the avalanche breakdown voltage, CMOS-compatible APD (CMOS-APD) exhibits negative photoconductance in photocurrent-voltage relationship and rf peaking in the photodetection frequency response. The reflection coefficient measurement of CMOS-APD indicates that rf peaking is due to resonance caused by appearance of inductive components in avalanche region. The rf-peaking frequency increases with the increasing reverse bias voltage.

Characterization of phototransistor internal gain in metamorphic high-electron-mobility transistors

We characterize the phototransistor internal gain of metamorphic high-electron-mobility transistors (mHEMTs). When the mHEMT operates as a phototransistor, it has internal gain provided by the photovoltaic effect. To determine this internal gain, photoresponse characteristics dominated by the photoconductive effect as well as the photovoltaic effect are investigated. When the device is turned off, it acts as a photoconductor, and by calculating photoconductor gain, the primary photodetected power can be determined, which indicates the absorbed optical power. The ratio between this and the photodetected power due to the photovoltaic effect represents phototransistor internal gain. It is demonstrated that the phototransistor internal gain is function of optical modulation frequency.

Phototransistors based on InP HEMTs and their applications to millimeter-wave radio-on-fiber systems

Phototransistors based on InP high electron-mobility transistors (HEMTs) are investigated for millimeter-wave radio-on-fiber system applications. By clarifying the photodetection mechanism in InP HEMTs, the phototransistor internal gain is determined. We present their use as millimeter-wave harmonic optoelectronic mixers and characterize them at the 60-GHz band. In order to evaluate the InP HEMT optoelectronic mixer performance, internal conversion gain is introduced and a maximum of 17 dB is obtained for 60-GHz harmonic optoelectronic up-conversion. Utilizing them, we construct a 60-GHz radio-on-fiber system and demonstrate 622-Mb/s data transmission over 30-km single-mode fiber and 3-m free space at 60-GHz band.

High optical responsivity of InAlAs-InGaAs metamorphic high-electron mobility transistor on GaAs substrate with composite channels

The high optical responsivity of the InAlAs-InGaAs metamorphic high-electron mobility transistor on GaAs substrate with composite channels is reported. Experimental results verify that the photovoltaic effect causing the effective decrease of threshold voltage is responsible for the photoresponse to a 1.55-/spl mu/m optical illumination.

Equivalent Circuit Model for Si Avalanche Photodetectors Fabricated in Standard CMOS Process

We present an equivalent circuit model for CMOS-compatible avalanche photodetectors. The equivalent circuit model includes an inductive component for avalanche delay, a current source for photogenerated carriers, and several components that model the device structure and parasitic effects. The model provides accurate impedance characteristics and photodetection frequency responses.

High-Speed CMOS Integrated Optical Receiver With an Avalanche Photodetector

We present a high-speed monolithically integrated optical receiver fabricated with 0.13-mum standard complementary metal-oxide-semiconductor (CMOS) technology. The optical receiver consists of a CMOS-compatible avalanche photodetector (CMOS-APD) and a transimpedance amplifier (TIA). The CMOS-APD provides high responsivity as well as large bandwidth. Its bandwidth is further enhanced by the TIA having negative capacitance, which compensates undesired parasitic capacitance. With the CMOS integrated optical receiver, 4.25-Gb/s optical data are successfully transmitted with a bit-error rate less than 10-12 at the incident optical power of - 5.5 dBm.

Self-Oscillating Harmonic Opto-Electronic Mixer Based on a CMOS-Compatible Avalanche Photodetector for Fiber-Fed 60-GHz Self-Heterodyne Systems

A self-oscillating harmonic opto-electronic mixer based on a CMOS-compatible avalanche photodetector for fiber-fed 60-GHz self-heterodyne systems is demonstrated. The mixer is composed of an avalanche photodetector fabricated with 0.18-mum standard CMOS process and an electrical feedback loop for self oscillation. It simultaneously performs photodetection and frequency up-conversion of photodetected signals into the second harmonic self-oscillation frequency band. The avalanche photodetector and the mixer are characterized and analyzed, and the RF avalanche multiplication factor is investigated. In addition, conversion efficiency as well as internal conversion gain is determined, and bias conditions are optimized for the best self-oscillating harmonic opto-electronic mixer performance. Data transmission of 5-MS/s 32 quadrature amplitude modulation signals using self-oscillating harmonic opto-electronic mixer is successfully demonstrated.

CMOS-compatible 60 GHz Harmonic Optoelectronic Mixer

We present 60 GHz harmonic optoelectronic mixers based on Si avalanche photodetectors (APDs) fabricated by the standard complementary metal-oxide-semiconductor (CMOS) technology. The characteristics of APDs and harmonic optoelectronic mixers are investigated in order to optimize their performances. At the avalanche on-set voltage of APD, efficient harmonic optoelectronic mixing at 60 GHz band is obtained. In order to demonstrate the feasibility of applying harmonic optoelectronic mixers for fiber-supported millimeter-wave communication systems, down-link data transmission of 5 MS/s, 32 quadrature modulation (QAM) signals in 60 GHz band is successfully performed.

Millimeter-wave Optoelectronic Mixers Based on CMOS-Compatible Si Photodetectors

We present millimeter-wave optoelectronic mixers based on Si photodetectors fabricated by the standard 130 nm complementary metal-oxide-semiconductor (CMOS) process. The photodetector and optoelectronic mixer characteristics are investigated in order to optimize their performances. Using the avalanche process in photodetectors at high reverse bias voltages, efficient optoelectronic mixing with low conversion loss at 30 GHz band is obtained. In order to demonstrate the feasibility of applying this mixer for radio-on-fiber (RoF) applications, detection and frequency up-conversion of optical 5 MS/s, 16 quadrature amplitude modulation (QAM) signals into the 30 GHz band is successfully performed. We believe this is the first report of using CMOS-compatible photodetectors for RoF applications

Low-Cost Multistandard Radio-Over-Fiber Downlinks Based on CMOS-Compatible Si Avalanche Photodetectors

We demonstrate a radio-over-fiber downlink based on a silicon avalanche photodetector (APD) fabricated with 0.18-mum standard complementary metal-oxide-semiconductor (CMOS) technology. An 850-nm vertical-cavity surface-emitting laser is used to deliver multistandard services including 2.1-GHz wideband code-division multiple access and 2.4-GHz IEEE 802.11g wireless local area network signals over 300-m multimode fiber. These signals are successfully detected by a CMOS-compatible APD (CMOS-APD) and then transmitted to a mobile terminal via wireless link. The error vector magnitude performance of each type of signal with the coexisting interferer is investigated.