We discuss a new simple InGaAs/InAlAs avalanche photodiode (APD) with a planar buried multiplication region. Some of the advantages compared to standard APDs are: 1. The thickness of the avalanche and the charge control regions are accurately controlled by molecular beam epitaxy (MBE) growth in contrast to the standard diffusion process; 2. InAlAs is the multiplication material (avalanching faster electrons) instead of InP (avalanching slower holes); 3. InAlAs avalanche gain has a lower noise figure than that for InP; 4. A guard ring is not required; 5. Fabrication is as simple as that for a p-i-n detector; 6. The APD has high wafer uniformity, and high reproducibility; 7. The InAlAs breakdown voltage is lower than InP, and its variation with temperature is three times lower than that for InP; 8. Excellent aging and reliability including Telcordia GR-468 qualification for die and modules; 9. High gain-bandwidth product as high as 150GHz; and 10.High long range (LR-2) bit error rate (BER) 10<sup>-12</sup> receiver sensitivity of -29.0dBm at 10Gb/s, -28.1dBm at 10.7Gb/s and -27.1dBm at 12.5Gbs.
The advances in parallel optical transmitter and receiver array technologies for large computing applications are described. Parallel data lines with 16 and 32 channels, with each channel operating at 1 Gb/s and 500 Mb/s respectively, have been demonstrated.
We discuss the development and the performances of a very long wavelength (13.5 - 15 micrometer) 128 by 128 AlGaAs/GaAs multiquantum well infrared imaging system. A highly uniform, high-yield QWIP focal plane array was hybridized to a CMOS multiplexer operating in a direct injection mode. For efficient light coupling an integral random scattering reflector (random grating) was incorporated. Due to the high uniformity, excellent imagery, low noise as well as a noise equivalent temperature difference (NE(Delta) T) of less than 30 mK were obtained when operating around 45 K. Therefore, high image contrast signal to noise ratio has been achieved.
We have fabricated and measured detailed bit error rate experiments on a 12 channel parallel optical interconnect transmitter operating at 1 Gb/s per channel, using InGaAsP/InP (lambda) equalsQ 1.3 micrometers lasers. The lasers are highly uniform, the channel crosstalk is less than 1 dB, and the mode selective losses are low (< 1 dB). This transmitter has been demonstrated in an architecture which would allow the transmission of 120 channels of 100 Mb/s uncompressed video signals. We have also demonstrated a novel high speed high quantum efficiency CMOS compatible Si MSM detector which would be ideal for monolithically integrated receiver arrays.
An Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As/GaAs quantum well infrared photodetector (QWIP) 128 X 128 focal plane array, incorporating integral grating structures for efficient optical coupling have been hybridized to silicon CMOS multiplexes. The demonstrated high uniformity, excellent detectivity, and high yield of operating pixels (99% plus) has resulted in excellent imagery in the 8 - 12 micrometers range, with a low noise equivalent temperature difference (NE(Delta) T) of less than 10 mK, and high image contrast signal to noise ratios (CSNR). We will discuss the figures of merit that govern the image quality in our QWIP focal plane arrays, such as D<SUP>*</SUP>, uniformity, CSNR, maximum input charge to the CMOS multiplex, etc. Our latest results will also be reported.
We discuss in detail the producibility issues associated with GaAs/Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As quantum well infrared photodetectors (QWIPs). Excellent uniformity in growth (thickness, doping, and Al concentration) and in processing are expected to lead to high yield, high performance large area infrared imaging arrays.
We discuss the physics and 128 X 128 array imaging performance of GaAs/AlxGa1-xAs n-doped quantum well infrared photodetectors (QWIPs). The device physics of novel p-doped QWIPs which respond to normal incidence radiation of also presented.
We demonstrate the first long wavelength quantum well infrared photodetectors (QWIPs) using lattice matched n-doped In0.47As/InP and n-doped 1.3 micrometers InGaAsP/InP materials systems. The responsivity of In0.52Ga0.47As/InP detectors has been found to be larger than that for similar GaAs/AlxGa1 - xAs detectors. In addition we demonstrate the first p-doped In0.53Ga0.47As/InP QWIPs. This detector has the shortest wavelength response, (lambda) p equals 2.7 micrometers , ever achieved in a QWIP and operates at normal incidence.
GaAs quantum-well IR photodetectors (QWIPs) that operate at a range of peak absorption wavelengths are considered in terms of their characteristics and potential applications. The structures of some QWIPs are described with references to their band diagrams, absorption coefficients, low-temperature quantum efficiencies, and peak detectivities. Peak detectivity is shown to be temperature- and bias-dependent and to be linked to doping density, and the QWIP technology in general has high peak detectivities and good uniformity for the production of large-area 2D arrays.
Graded band gap ITT-V semiconductor structures have been grown by molecular beam epitaxy using
electron beam evaporation of Group III metals. The deposition rates of the Group III metals are measured and
controlled in real-time using Inficon Sentinel III rate monitors. The rapid response of the electron beam
evaporation sources allows precise alloy grading over distances as short as 1 nm. A variety of novel 111-V device
structures have been realized by this technique.