IntelliEPI (United States)

Accurate measurement of substrate temperature is one of the most critical process control parameters for molecular beam epitaxy (MBE) growth. Band-edge thermometry instruments have proven to be a valuable tool for process control during MBE growth of semiconductor films, providing as high as ±1 °C temperature resolution. The increasing use of InAs, GaSb, and AlSb iii-v materials necessitates a method for accurately measuring the temperature of their closely lattice-matched GaSb substrates. Current-technology instruments typically rely on InGaAs detector materials which have a maximum wavelength λ detection of ∼1.7 μm, but GaSb substrates have a band gap energy corresponding to λ > 2 μm. A band-edge thermometry instrument capable of λ > 2 μm has been developed using an InAs/InGaSb strained-layer superlattice detector sensitive to 2-9.5 μm long-wave IR wavelengths.

■ Classic controller design + evolutionary optimization approach ■ Suitability of evolutionary optimization was successfully tested ■ Possible reusability of evolutionary algorithms ■ Further HW-accelerated implementation and online FCS autotuning

We report studies of two key factors involved in the use of MnAs as a spin injector, namely, Mn diffusion and spin injection properties when it is grown on GaAs-based semiconductor heterostructures. Depth profile of Mn concentration in a sample consisting of a MnAs film grown on GaAs is investigated with time-of-flight secondary ion mass spectroscopy. The result shows that Mn diffusion into GaAs is negligible, unlike the case of Ga1−xMnxAs/GaAs, in which Mn diffusion is significant. Meanwhile, robust spin injection is observed with MnAs as a spin injector for a GaAs-based light emitting diode, persisting up to room temperature.

We present structural, optical, and transport characterization of long wave infrared hot electron transistor (IHET) based on doped quantum wells of InGaAs/AlGaAs. The atomic resolution images and x-ray diffraction patterns verified a lattice matched and band-gap engineered device structure of IHET. Measured values of the photocurrent were less than the theoretically expected values and indicated a loss of photocurrent between the base of the IHET and the collector. A higher filter height due to high unexpected dopant in the filter barrier was suggested as a possible cause of the current loss. Photoluminescence data in the near infrared showed the existence of such a dopant.

We demonstrated optoelectronic mixers, which are constructed from near-ballistic uni-traveling-carrier photodiodes and band-pass filters. By utilizing strong nonlinearity of electron ballistic-transport, such module achieves low-up-conversion-loss (4.3 dB) and wide-up-conversion-bandwidth (11 GHz) under high-optical-power injection (16.6 dBm) at 30 GHz.

This paper reports on the design, growth, fabrication, and processing of an integrated Grating-Outcoupled Surface Emitting (GSE) semiconductor laser and a Double Heterojunction Bipolar Transistor (DHBT) driver. The GSE laser has a 380 mum long gain section, 15 mum long out-coupler, and 200 mum long distributed Bragg reflectors (DBRs). The design of the DHBT includes an InP emitter and collector and an InGaAs carbon doped base layer. Advantages of electronic-photonic integrated circuits (EPICs) include 1) increased speed, 2) lower noise, 3) reduced power requirements since the driver and laser no longer need to be matched to a 50-ohm transmission line, 4) on-wafer testing capability and mapping of known good die, 5) reduced packaging costs, and 6) improved reliability.

We have developed novel but simple process techniques for high speed InP SHBTs. For parasitic reduction, the collector layer is undercut using an etch-stop layer, the base pad is isolated, and the emitter metal is widened using thick plated gold. For transit time reduction, the SHBT employs InGaAs base with graded In-composition and InGaAlAs emitter setback with graded Al-composition. Maximum extrapolated f/sub max/ of about 687 GHz with f/sub T/ of 215 GHz is achieved for 0.25 /spl times/ 8 /spl mu/m/sup 2/ emitter area devices at I/sub c/ = 8 mA and V/sub ce/ = 15 V. This data clearly shows that the optimized conventional process can offer direct implementation of InP HBT for high-speed electronic circuit fabrication.

Ground-based optical transmitter and receiver systems designed for active imaging, active tracking and laser ranging of satellites in Earth orbit are very sensitive to physical conditions limiting the radiometric returns for achieving these measurements. The initial design of these systems is often based on simple radiometric scaling laws that provide estimates of average radiometric returns and are derived from experimental data or from more complex theoretical calculations. While these laws are quite useful, it is often easy to lose sight of the initial assumptions made in their formulation, and hence, the limits of their accuracy for designing certain systems. The objective of this paper is to review some of the commonly used radiometric scaling laws for active systems and to establish guidelines for their use based on comparisons of their predictions with results from detailed wave-optics simulations for different system design requirements and physical conditions. The combined effects of laser and transmitter beam parameters, wave-front aberrations, atmospheric turbulence, and satellite optical cross-section are considered.