D. H. Chow

Auger lifetime enhancement in InAs–Ga1−xInxSb superlattices

We have experimentally and theoretically investigated the Auger recombination lifetime in InAs–Ga1−xInxSb superlattices. Data were obtained by analyzing the steady‐state photoconductive response to frequency‐doubled CO2 radiation, at intensities varying by over four orders of magnitude. Theoretical Auger rates were derived, based on a k⋅p calculation of the superlattice band structure in a model which employs no adjustable parameters. At 77 K, both experiment and theory yield Auger lifetimes which are approximately two orders of magnitude longer than those in Hg1−xCdxTe with the same energy gap. This finding has highly favorable implications for the application of InAs–Ga1−xInxSb superlattices to infrared detector and nonlinear optical devices.

Physics-based RTD current-voltage equation

An analytic expression for the current-voltage characteristics of resonant tunneling diodes is derived from basic principles. The form is ideal for insertion into circuit simulation models. It is demonstrated for a conventional InGaAs-AlAs RTD and for an InAs-AlSb-GaSb RIT diode. The expression is based on the quantum tunneling formalism and contains parameters that originate from physical quantities, but which can also be treated as empirical. Empirical fitting is straightforward and results in an excellent match to the data. Additional levels of physical realism can be incorporated in a natural way.

Mid-wave infrared diode lasers based on GaInSb/InAs and InAs/AlSb superlattices

We report the characterization of a set of broad‐area semiconductor diode lasers with mid‐wave infrared (3–5 μm) emission wavelengths. The active region of each laser structure is a 5‐ or 6‐period multiple quantum well (MQW) with Ga0.75In0.25As0.22Sb0.78 barriers and type‐II (broken‐gap) Ga0.75In0.25Sb/InAs superlattice wells. The cladding layers of each laser structure are n‐ and p‐type InAs/AlSb (24 A /24 A) superlattices grown lattice‐matched to a GaSb substrate. By tailoring constituent layer thicknesses in the Ga0.75In0.25Sb/InAs superlattice wells, laser emission wavelengths ranging from 3.28 μm (maximum operating temperature=170 K) to 3.90 μm (maximum operating temperature=84 K) are obtained.

GaN HFET for W-band Power Applications

In this paper we report high frequency GaN power device and measured power performance of the first W-band (75 GHz-110 GHz) MMIC fabricated in GaN material system. The first W-band GaN MMIC with 150 mum of output gate periphery produces 316 mW of continuous wave output power (power density =2.1 W/m) at a frequency of 80.5 GHz and has associated power gain of 17.5 dB. By comparison the reported state of the art for other solid state technologies in W-band is 427 mW measured in a pulsed mode on an InP HEMT MMIC with 1600 mum of output periphery (power density = 0.26 W/mm). The reported result demonstrates tremendous superiority of GaN device technology for power applications at frequencies greater than 75 GHz

Midwave infrared stimulated emission from a GaInSb/InAs superlattice

Use of a cracked Sb source and a postgrowth anneal procedure has been found to yield significant improvements in optical efficiencies of GaInSb/InAs superlattices grown by molecular beam epitaxy. Appreciable 5 μm band‐to‐band luminescence has been observed at room temperature, and stimulated emission at 3.2 μm has been demonstrated in an optically pumped structure. Intrinsic properties of this class of superlattices favor them for application as efficient infrared lasers operating at comparatively high temperatures.

12 GHz clocked operation of ultralow power interband resonant tunneling diode pipelined logic gates

We report on the successful demonstration of a functionally complete set of logic gates based on resonant interband tunneling diodes (RITDs) with a maximum operating frequency in excess of 12 GHz. At this high frequency of operation, the power dissipation is remarkably low-on the order of 0.5 mW per gate. The circuits for all gates, AND, OR, XOR, and INV, shared the same layout geometry, consisting of two Schottky diodes and three RITDs. Logical functionality was determined solely by varying the relative areas of the devices.

92–96 GHz GaN power amplifiers

We report the test results of a family of 92-96 GHz GaN power amplifiers (PA) with increasing gate peripheries (150 µm to 1200 µm). The 1200 µm, 3-stage PA produces 2.138 W output power (Pout) with an associated PAE of 19% at 93.5 GHz (VD=14V). The amplifier offers Pout over 1.5W with associated PAE over 17.8% in the 92–96 GHz bandwidth. The measured data show that the maximum Pout scales linearly with increasing gate periphery at an almost constant PAE around 20%. This demonstrates the high efficiency of on-chip power combining and enables W-band high power single chip solid state power amplifiers.

W-Band GaN MMIC with 842 mW output power at 88 GHz

We report W-band GaN MMICs that produce 96% more power at a frequency of 88 GHz in continuous wave (CW) operation than the highest power reported in this frequency band for the best competing solid state technology[1], the InP HEMT. W-band power module containing a single three stage GaN MMIC chip with 600 µm wide output stage produced over 842 mW of output power in CW-mode, with associated PAE of 14.7% and associated power gain of 9.3 dB. This performance was measured at MMIC drain bias of 14 V.

1.7-ps, microwave, integrated-circuit-compatible InAs/AlSb resonant tunneling diodes

Microwave integrated-circuit-compatible InAs/AlSb resonant tunneling diodes (RTDs) have been fabricated. The resulting devices have peak current densities of 3.3*10/sup 5/ A/cm/sup 2/ with peak-to-valley ratios of 3.3. Switching transition times of 1.7 ps are measured using electrooptic sampling techniques.<<ETX>>

GaN MMIC technology for microwave and millimeter-wave applications

In this paper we demonstrate the merits of GaN MMIC technology for high bandwidth millimeter-wave power applications and for microwave robust LNA receiver applications. We report the development of a broadband two-stage microstrip Ka-band GaN MMIC power amplifier, with 15dB of flat small signal gain over the 27.5GHz to 34.5GHz frequency range and 4W of saturated output power at 28GHz, with a power added efficiency of 23.8%. This is to the best of our knowledge the best combination of output power, bandwidth and efficiency reported for a GaN MMIC in Ka-band frequency range. We also report a robust two-stage wideband (0.5GHz-12GHz) GaN LNA MMIC, which can survive 4W of incident input RF power in CW mode without input power protective circuitry. The presented LNA MMIC has, to the best of our knowledge, the best combination of NF, bandwidth, survivability and low power consumption reported to date in GaN technology.