Si-based resonant-cavity-enhanced photodetector

We report one top-illumination and one bottom-illumination SiGe/Si multiple quantum-well (MQW) resonant-cavity-enhanced (RCE) photodetector fabricated on a separation-by-implanted-oxygen (SIMOX) wafer operating near 1300 nm. The buried oxygen layer in SIMOX is used as a mirror to form a vertical cavity with the silicon dioxide/silicon Bragg reflector deposited on the top surface. A peak responsivity with a reverse bias of 5 V is measured 10.2 mA/W at 1285 nm, a full width at half maximum of 25 nm for the top-illumination RCE photodetector, 19 mA/W at 1305 nm, and a full width at half maximum of 14 nm for the bottom-illumination one. The external quantum efficiency of the bottom-illumination RCE photodetector is up to 2.9% at 1305 nm, with a reverse bias of 25V. The responsivity of the bottom-illumination RCE photodetector is improved by two-fold compared with that of the top-illumination one. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

Back-incident SiGe-Si multiple quantum-well resonant-cavity-enhanced photodetectors for 1.3-mu m operation

A back-incident Si-0.65 Ge-0.35/Si multiple quantum-well resonant-cavity-enhanced photodetector operating near 1.3 mum is demonstrated on a separation-by-implantation-oxygen substrate. The resonant cavity is composed of an electron-beam evaporated SiO2-Si distributed Bragg reflector as a top mirror and the interface between the buried SiO2 and the Si substrate as a bottom mirror. We have obtained the responsivity as high as 31 mA/WI at 1.305 mum and the full width at half maximum of 14 nm.

Si1-xGex/Si resonant-cavity-enhanced photodetectors with a silicon-on-oxide reflector operating near 1.3 mu m

We report on a Si1-xGex/Si multiple quantum-well resonant-cavity-enhanced (RCE) photodetector with a silicon-on-oxide reflector as the bottom mirror operating near 1.3 mu m. The breakdown voltage of the photodetector is above 18 V and the dark current density at 5 V reverse bias is 12 pA/mu m(2). The RCE photodetector shows enhanced responsivity with a clear peak at 1.285 mu m and the peak responsivity is measured around 10.2 mA/W at a reverse bias of 5 V. The external quantum efficiency at 1.3 mu m is measured to be 3.5% under reverse bias of 16 V, which is enhanced three- to fourfold compared with that of a conventional p-i-n photodetector with a Ge content of 0.5 reported in 1995 by Huang [Appl. Phys. Lett. 67, 566 (1995)]. (C) 2000 American Institute of Physics. [S0003-6951(00)00628-8].

Characteristics of circular waveguide photodetectors using SiGe/Si multiple quantum wells

We report on the fabrication of circular waveguide photodetectors with a response near 1.3 mu m wavelength using SiGe/Si multiple quantum wells. The quantum efficiency of the circular waveguide photodetector is improved when compared with that of the rib waveguide photodetector in the same wavelength at 1.3 mu m The frequency response of the photodetectors is simulated. The emciency-bandwidth product of the circular waveguide photodetectors is improved correspondingly. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

A New Edge-Coupled Two-Terminal Double Heterojunction Phototransistor (ECTT-DHPT) and Its DC Characteristics

A new ECTT-DHPT with InGaAsP(lambda=1.55 mu m) as base and InGaAsP(lambda=1.3 mu m) as collector as well as waveguide was designed and fabricated, the DC characteristics reveal that the ECTT-DRPT can perform good optoelectronic mix operation and linear amplification operation by optically biased at two appropriate value respectively. Responsivity of more than 52A/W and dark current of 70nA (when V-ce=1V) were obtained.

Si-based membrane resonant cavity enhanced photodetectors

Si-based membrane RCE photodetectors were introduced. The RCE photodiodes were fabricated on silicon membranes formed from SOI substrate. Compared with the conventional p-i-n photodiode, the responsivity has a threefold enhancement.

1.55-mu m resonant cavity enhanced photodiode based on MBE grown Ge quantum dots

Self-assembly Ge quantum dots (QD) on Si and Si/Ge mutli-quantum-wells (MQW) are grown by MBE. The island size and island density was investigated by atomics force microscopy. Ten-layer and twenty-layer MQW were selected for photodiode device fabrication. In photoluminescence (PL), a broad peak around 1.55-mu m wavelength was observed with higher peak intensity for the 10-layer MQW which had less defects than the 20-layer sample. Resonant cavity enhanced (RCE) photodiodes were fabricated by bonding on a SOI wafer. Selected responsivity at 1.55 mu m was successfully demonstrated. (c) 2005 Elsevier B.V. All rights reserved.

1.55 mu m Ge islands resonant-cavity-enhanced narrowband detector

The high quality Ge islands material with 1.55 mu m photo-response grown on Sol substrate is reported. Due to the modulation of the cavity formed by the mirrors at the surface and the buried SiO2 interface, seven sharp and strong peaks with narrow linewidth are found. And a 1.55 mu m Ge islands resonant-cavity-enhanced (RCE) detector with narrowband was fabricated by a simple method. The bottom mirror was deposited in the hole formed by anisotropically etching, in a basic solution from the backside of the sample with the buried SiO2 layer in silicon-on-insulator substrate as the etch-stop layer. Reflectivity spectrum indicates that the mirror deposited in the hole has a reflectivity as high as 99% in the range of 1.2-1.65 mu m. The peak responsivity of the RCE detector at 1543.8 nm is 0.028 mA/W and a full width at half maximum of 5 nm is obtained. Compared with the conventional p-i-n photodetector, the responsivity of RCE detector has a nearly threefold enhancement.

Design and Characterization of Evanescently Coupled Uni-Traveling Carrier Photodiodes with a Multimode Diluted Waveguide Structure

A new evanescently coupled uni-traveling carrier photodiode (EC-UTC-PD) is designed, fabricated and characterized, which incorporates a multimode diluted waveguide structure and UTC active waveguide structure together. A high responsivity of 0.68A/W at 1.55-mu m without an anti-reflection coating, a linear photocurrent responsivity of more than 21 mA, and a large-1 dB vertical alignment tolerance of 2.5 mu m are achieved.

Abnormal photoabsorption in high resistance GaN epilayer

Unintentionally doped GaN epilayers are grown by the metalorganic chemical vapor deposition (MOCVD). Photovoltaic (PV) spectroscopy shows that there appears an abnormal photoabsorption in some undoped GaN films with high resistance. The peak energy of the absorption spectrum is smaller than the intrinsic energy band gap of GaN. This phenomenon may be related to exciton absorption. Then metal-semiconductor-metal (MSM) Schottky photodetectors are fabricated on these high resistance epilayers. The photo spectrum responses are different when the light individually irradiates each of the two electrodes with the photodetector which are differently biased. When the excitation light irradiates around the reverse biased Schottky junction, the responsivity is almost one order of magnitude larger than that around the forward biased junction. Furthermore, when the excitation light irradiates the reverse biased Schottky junction, the peak energy of the spectrum has a prominent red-shift compared with the peak energy of the spectrum measured with the excitation light irradiating the forward biased Schottky junction. The shift value is about 28 meV, and it is found to be insensitive to temperature. According to the analyses of the distribution of the electric field within the MSM device and the different dependences of the response on the electric field intensity between the free carriers and excitons, a reliable explanation for the different response among various areas is proposed.

A high-efficiency high-power evanescently coupled UTC-photodiode

The effects of the multimode diluted waveguide on quantum efficiency and saturation behavior of the evanescently coupled uni-traveling carrier(UTC)photodiode structures are reported. Two kinds of evanescently coupled uni-traveling carrier photodiodes(EC-UTC-PD)were designed and characterized: one is a conventional EC-UTC-PD structure with a multimode diluted waveguide integrated with a UTC-PD; and the other is a compact EC-UTC-PD structure which fused the multimode diluted waveguide and the UTC-PD structure together. The effect of the absorption behavior of the photodiodes on the efficiency and saturation characteristics of the EC-UTC-PDs is analyzed using 3-D beam propagation method, and the results indicate that both the responsivity and saturation power of the compact EC-UTC-PD structures can be further improved by incorporating an optimized compact multimode diluted waveguide.

A High-Efficiency Fiber-to-Waveguide Coupler with Low Polarization Dependence Using a Diluted Waveguide in InP Substrate with a 1.55μm Wavelength

We propose a fiber-to-waveguide coupler for side-illuminated p-i-n photodiodes to obtain high responsivity and low polarization dependence that is grown on InP substrate and is suitable for surface hybrid integration in low cost modules. The fiber-to-waveguide coupler is based on a diluted waveguide,which is composed of ten periods of undoped 120nm InP/80nm InGaAsP （1.05μm bandgap） multiple layers. Using the semi-vectorial three dimensional beam propagation method （BPM） with the central difference scheme,the coupling efficiency of fiber-to-waveguide under different conditions is simulated and studied,and the optimized conditions for fiber-to-waveguide coupling are obtained. For TE-like and TM-like modes,the calculated maximum coupling efficiency is higher than 94% and 92% ,respectively. The calculated polarization dependence is less than 0. ldB,showing good polarization independence.

A High Speed, 12-Channel Parallel, Monolithic Integrated CMOS OEIC Receiver

The design and fabrication of a high speed, 12-channel monolithic integrated CMOS optoelectronic integrated circuit(OEIC) receiver are reported.Each channel of the receiver consists of a photodetector,a transimpedance amplifier,and a post-amplifier.The double photodiode structure speeds up the receiver but hinders responsivity.The adoption of active inductors in the TIA circuit extends the-3dB bandwidth to a higher level.The receiver has been realized in a CSMC 0.6μm standard CMOS process.The measured results show that a single channel of the receiver is able to work at bit rates of 0.8～1.4Gb/s. Altogether, the 12-channel OEIC receiver chip can be operated at 15Gb/s.

Fabrication of SiGe/Si Multi-Quantum Wells Resonant-Cavity-Enhanced Detector

A SiGe/Si multi-quantum wells resonant-cavity-enhanced(RCE) detector with high reflectivity bottom mirror is fabricated by a new method.The bottom mirror is deposited in the hole,which is etched from the backside of the sample by ethylenediamine-pyrocatechol-water(EPW) solution with the buried SiO2 layer in SOI substrate as the etching-stop layer.Reflectivity spectrum indicates that the mirror deposited in the hole has a reflectivity as high as 99% in the range of 1.2～1.5μm.The peak responsivity of the RCE detector at 1.344μm is 1.2mA/W and the full width at half maximum is 12nm.Compared with the conventional p-i-n photodetector,the responsivity of RCE detector is enhanced 8 times.

Asymmetric dark current in double barrier quantum well infrared photodetectors

Asymmetric dark current and photocurrent versus voltage characteristic in the Double Barrier Quantum Wells (DBQWs) photovoltaic infrared photodetector has been studied. A model based on asymmetric potential barriers was proposed. The asymmetric potential thick barrier, which due to the Si dopant segregation during growth makes a major contribution to the asymmetrical I-V characteristic, calculations based on our model agree well with experimental results. This work also confirms the potential use of this DBQWs for infrared photodetector with large responsivity and little dark current under negative bias.