Coherent Ge quantum dots embedded in Si spacing layers were grown on Si substrate by molecular-beam epitaxy in the Stranski–Krastanov mode. Photoluminescence measurement showed a Ge-dot-related peak at 1.46 μm. p-i-n photodiodes with the intrinsic layer containing Ge dots were fabricated, and current–voltage (I–V) measurement showed a low dark current density of 3×10−5 A/cm2 at −1 V. A strong photoresponse at 1.3–1.52 μm originating from Ge dots was observed, and at normal incidence, an external quantum efficiency of 8% was achieved at −2.5 V.

Normal-incidence Ge quantum-dot photodetectors at 1.5 μm based on Si substrate

A theoretical model incorporating the mechanism of resonant absorption of the multiple reflected lightwaves is presented for the frequency response of resonant-cavity (RC) separate absorption, charge, and multiplication (SACM) avalanche photodiodes (APDs). The derived theoretical expressions are general and can be readily applied to many other RC and non-RC APDs. These analytical expressions also allow for fast computation of the frequency response and bandwidth characteristics. Combining this frequency response theory with expressions of multiplication gain and ionization coefficients, an efficient approach is proposed for modeling the general performance characteristics of RC APDs. The modeling approach is applied to an InGaAs-AlGaAs RC SACM APD. The computed results are demonstrated, and the results of -3 dB bandwidth are comparable to experimental work. The validity of the modeling parameters is also discussed. It is further found that the normalized frequency response is unaffected when the value of the absorption coefficient is changed, suggesting that the standing-wave effect within the RC structure may not influence the bandwidth characteristics.

Frequency response and modeling of resonant-cavity separate absorption, charge, and multiplication avalanche photodiodes

A 155 mum Ge islands resonant-cavity-enhanced (RCE) detector with high-reflectivity bottom mirror was fabricated by a simple method The bottom mirror was deposited in the hole formed by anisotropically etching in a basic solution from the back side 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 12-165 mum The peak responsivity of the RCE detector at 15438 nm is 0028 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 (C) 2004 American Institute of Physics

1.55μmGe islands resonant-cavity-enhanced detector with high-reflectivity bottom mirror

A SiGe/Si multiple-quantum-well resonant-cavity-enhanced (RCE) photodetector for 1.3 μm operation was fabricated using bonding reflector process. A full width at half maximum (FWHM) of 6 nm and a quantum efficiency of 4.2% at 1314 nm were obtained. Compared to our previously reported SiGe RCE photodetectors fabricated on separation-by-implanted-oxygen wafer, the mirrors in the device can be more easily fabricated and the device can be further optimized. The FWHM is expected to be less than 1 nm and the detector is fit for density wavelength division multiplexing applications.

SiGe/Si resonant-cavity-enhanced photodetectors for 1.3 μm operation fabricated using wafer bonding techniques

A near-infrared waveguide photodetector in a Si-based ternary Si 1 - x - y Ge x C y alloy is analyzed theoretically and the simulation results are obtained for 0.85- to 1.06-μm wavelength fiber optic interconnection system applications. Two sets of detectors with active absorption layer compositions of Si 0 . 7 9 Ge 0 . 2 C 0 . 0 1 and Si 0 . 7 0 Ge 0 . 2 8 C 0 . 0 2 are designed. The active absorption layer has a thickness of 120 to 450 nm. The external quantum efficiency can reach ∼3% with a cut-off wavelength of around 1.2 μm.

Theoretical analysis of Si1−x−yGexCy near-infrared photodetectors

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].

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

We report the results of a high efficiency room temperature continuous wave (cw) vertical‐cavity surface‐emitting laser. The structure is obtained by four deep H+ implantation using tungsten wires as the mask. The fabrication process is the simplest ever reported in vertical‐cavity surface‐emitting laser fabrication. The largest differential quantum efficiency of 65% and maximum cw light output power over 4 mW have been achieved for the 15×15 μm2 device.

High efficiency top surface‐emitting lasers fabricated by four implantation using tungsten wire as mask

Resonant-cavity-enhanced photodetectors have been demonstrated to be able to improve the bandwidth-efficiency product. We report a novel SiGe/Si multiple quantum-well resonant-cavity-enhanced photodetector fabricated on a separation-by-implanted-oxygen wafer operating near 1300nm. The buried oxide layer in SIMOX is used as a bottom mirror to form a vertical cavity with silicon dioxide/silicon Bragg reflector deposited on the top surface. The quantum efficiency at the wavelength of 1300nm is measured with 3.5% at a reverse bias of 15V, which is enhanced by 10 folds compared with a conventional photodetector with the same absorption structures.

SiGe/Si quantum well resonant-cavity-enhanced photodetector

Due to the potential barriers in the heterointerfaces of quarter wavelength stack layers of the distribute Bragg reflector (DBR) in vertical cavity surface emitting lasers, P-DBR has a very large series resistance. The paper reported a method of reducing this series resistance by Zn diffusion. By this way, we have achieved continue wave vertical cavity surface emitting lasers.

Application of Zn diffusion in reducing the series resistance of the P-distributed Bragg reflector in GaAs/GaA1As vertical cavity surface emitting lasers

The effects of the thickness of the oxidized layer, reaction temperature and carrier gas flow on the oxidation rate of Al x Ga 1-x As-AlAs-GaAs heterostructures are presented. The electrically-pumped GaAs/AlGaAs vertical cavity surface emitting laser 2D arrays fabricated by selective etching and selective oxidation are described. The square current flow aperture of 4 X 4 micrometers 2 are formed by the buried oxidized AlAs layers formed on both top and bottom distributed Bragg reflectors adjacent active region. The serious resistance of the devices are 60 to 80 (Omega) . The continuous-wave threshold current as low as 3.8mA is obtained at room temperature. The devices show the maximum output power over 1mW. Their angles of divergence are less than 7.8 degrees and the pulse rise times are less than 100ps in the high speed pulse response measurements. The 2 X 3 2D arrays are obtained. The thresholds of devices in the array are within 6 +/- 0.5 mA.

Hongjie Wang

Papers

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

High efficiency top surface‐emitting lasers fabricated by four implantation using tungsten wire as mask

SiGe/Si quantum well resonant-cavity-enhanced photodetector

Application of Zn diffusion in reducing the series resistance of the P-distributed Bragg reflector in GaAs/GaA1As vertical cavity surface emitting lasers

VCSEL array fabricated by selective etching and selective oxidation