H.L. Dunlap

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.

InAs/AlSb/GaSb resonant interband tunneling diodes and Au-on-InAs/AlSb-superlattice Schottky diodes for logic circuits

Integrated resonant interband tunneling (RIT) and Schottky diode structures, based on the InAs/GaSb/AlSb heterostructure system, are demonstrated for the first time. The RIT diodes are advantageous for logic circuits due to the relatively low bias voltages (/spl sim/100 mV) required to attain peak current densities in the mid-10/sup 4/ A/cm/sup 2/ range. The use of n-type InAs/AlSb superlattices for the semiconducting side of Schottky barrier devices provides a means for tailoring the barrier height for a given circuit architecture. The monolithically integrated RIT/Schottky structure is suitable for fabrication of a complete diode logic family (AND, OR, XOR, INV).

An efficient HBT/RTD oscillator for wireless applications

In this paper, we introduce a novel HBT/RTD oscillator suitable for monolithic integration and efficient low power/battery-operated applications. Implementation of a circuit prototype was accomplished by configuring an InP-based monolithic HBT/RTD chip with a gold wire bond inductor in a hybrid microwave package. For an output frequency of 5.8 GHz, the circuit draws a current of 15.5 mA from a 1.5 V supply and generates an output power of +3.13 dBm, for an efficiency of 8.84%.

New tunnel diode for zero-bias direct detection for millimeter-wave imagers

High-resolution passive millimeter wave imaging cameras require per pixel detector circuitry that is simple, has high sensitivity, low noise, and low power. Detector diodes that do not require bias or local oscillator input, and have high cutoff frequencies are strongly preferred. In addition, they must be manufacturable in large quantities with reasonable uniformity and reproducibility. Such diodes have not been obtainable for W-band and above. We are developing zero-bias square-law detector diodes based on InAs/Alsb/GaAlSb heterostructures which for the first time offer a cost-effective solution for large array formats. The diodes have a high frequency response and are relatively insensitive to growth and process variables. The large zero- bias non-linearity in current floor necessary for detection arises from interband tunneling between the InAs and the GaAlSb layers. Video resistance can be controlled by varying an Alsb tunnel barrier layer thickness. Our analysis shows that capacitance can be further decreased and sensitivity increased by shrinking the diode area, as the diode can have very high current density. DC and RF characterization of these devices and an estimate of their ultimate frequency performance in comparison with commercially available diodes are presented.

Sb-heterostructure zero-bias diodes for direct detection beyond 100 GHz

We have developed a new kind of millimeter wave diode for zero-bias detection up to and beyond 100GHz. The diode is based on the InAs/GaSb/AlSb heterostructure, which has a staggered Type II band gap alignment in which the conduction band of the InAs is lower in energy than the GaSb valence band edge. This produces a built-in asymmetry which produces a high zero bias nonlinearity in the current-voltage characteristic. The heterostructure is a relatively simple one that is reliably and reproducibly grown using standard molecular beam epitaxy techniques. The diodes we have fabricated demonstrate that this is a new and superior solution as compared with its predecessors, the Ge backward diode and the planar doped barrier diode, for detection and mixing of small input power-level signals without the added complexity of DC bias or local oscillator.

High frequency performance of Sb-heterostructure millimeter-wave diodes

We have developed a new zero bias millimeter wave diode based on quantum tunneling in an InAs/AlSb/GaSb nanostructure. It is ideal for square law radiometry and passive millimeter wave imaging. Excellent sensitivity has been demonstrated at present up to 110 GHz, with higher bandwidth predicted for smaller area diodes.

DHBT/RTD-based active frequency multiplier for wireless communications

We present, for the first time, measured data pertaining the microwave performance and characterization of a X6 (127->762 MHz) active frequency multiplier (FM), based on AIInAs/GaInAs/InP double heterostructure bipolar transistor (DHBT) and AlAs/InGaAs resonant tunneling diode (RTD) active devices. At +23/spl deg/C and a nominal input power of -3 dBm, the X6 DHBT/RTD multiplier exhibits a conversion gain of +1 dB, a power dissipation of 22 mW, a dc efficiency of 3%, and an overall 0 to 60/spl deg/C output power variation of 0.7 dB. The rich output harmonic content makes the DHBT/RTD combination a prime candidate for high-order multiplication applications.

Sb-heterostructure millimeter-wave zero-bias diodes

Millimeter wave detection at W-band and above has great potential for imaging under a variety of environmental conditions such as precipitation, smoke, and dust. One current limiting factor is the large per pixel cost of arrays. Direct detecting zero bias diodes would reduce the cost significantly. Here, we demonstrate specially designed Sb-heterostructure-based backward diodes grown by molecular beam epitaxy. These diodes have superior frequency response compared to Ge diodes. The behavior is based on heterojunction tunneling and, in contrast to planar doped barrier (PDB) diodes, is not overly sensitive to growth conditions. Estimates indicate frequency operation comparable to or superior to PDB diodes should be achievable. Millimeter wave detector arrays containing thousands of diodes are now feasible for the first time at W-band and above. We present measurements demonstrating this performance and estimate the ultimate frequency potential of this new technology. The material system used is the InAs-AlSb-GaAlSb nearly lattice matched combination.