David Hoag

AlGaAs PIN diode multi-octave, mmW switches

The novel use of an AlGaAs/GaAs heterojunction to form a PIN diode, with reduced RF resistance (RS) and no change in junction capacitance (CT)[1]–[3], has been analyzed and employed in the development of several different PIN diode switches of various circuit topologies. Series designs demonstrate improved insertion loss, shunt designs improved isolation, and series-shunt designs improvements in both parameters. These switches demonstrate superior broadband performance, with low insertion loss and high isolation from 50MHz to almost 80GHz, and series-shunt switches exhibit 50% increased input power capability over equivalent homojunction GaAs PIN diode switches.

Heterojunction PIN diode switch

This paper describes the development of a heterojunction AlGaAs/GaAs PIN diode as a replacement for the homojunction GaAs PIN diodes commonly used in microwave systems as a control element for commercial and military switch applications up through millimeter wave frequencies. In particular, a single heterojunction PIN diode, when simulated at a bias of 10 mA in a 50 ohm series configuration, indicates a potential reduction in insertion loss of 37% (Rs) with no degradation in isolation (Cj). This paper describes a switch topology of choice which uses a series-shunt element at the main junction, since it offers the widest bandwidth due to the low zero bias capacitance of the series diode. This simple structure has an upper frequency limitation that is dependent on the electrical distance due to the physical location of the series diode relative to the center of the actual device junction and the maximum isolation achievable by the Cj of a discrete diode. PIN switch circuits and RF probable test structures were processed through our GaAs wafer fab and later tested on-wafer for broadband RF performance from 50 MHz through 40 GHz. A comparison between simulated and empirical results for insertion loss, return loss and isolation demonstrates excellent agreement for isolation and a 10% offset for insertion loss and return loss.

Ka band high power AlGaAs PIN diode switches

In this paper we present the design and performance of millimeter wave MMIC switches in the patented MA-COM AlGaAs heterojunction PIN Diode process that allow us to produce high power and low insertion loss devices. The design process from a reflective SPDT switch to a non-reflective version of the switch, with intense use of HFSS and ADS software, is presented. These switches were designed to meet demanding requirements: low insertion loss less than 0.8 dB, 40dBm peak power and 37dBm CW power, and 30dB isolation.

Characteristics of surface mount low barrier silicon Schottky diodes with boron contamination in the substrate–epitaxial layer interface

Unusual negative resistance characteristics were observed in low barrier HMIC (Heterolithic Microwave Integrated Circuit) silicon Schottky diodes with HF (hydrofluoric acid)/IPA (isopropyl alcohol) vapor clean prior to epitaxial growth of silicon. SIMS (secondary ion mass spectroscopy) analysis and the results of the buried layer structure confirmed boron contamination in the substrate/epitaxial layer interface. Consequently the structure turned into a thyristor like p-n-p-n device. A dramatic reduction of boron contamination was found in the wafers with H20/HCl/HF dry only clean prior to growth, which provided positive resistance characteristics. Consequently the mean differential resistance at 10 mA was reduced to about 8.1 ?. The lower series resistance (5.6?5.9 ?) and near 1 ideality factor (1.03?1.06) of the Schottky devices indicated the good quality of the epitaxial layer.

Novel thyristor-based microwave cross-point switch MMIC

A novel GaAs 16 /spl times/ 16 cross-point switch monolithic microwave integrated circuit (MMIC) is presented. The switch MMIC incorporates 256 GaAs microwave thyristor devices as switching elements. The thyristors are two-terminal devices with anodes connected to a common horizontal electrode and cathodes connected to a common vertical electrode. Bistable operation of the thyristors permits x-y addressing at the edge of the chip to turn on and off each thyristor. Applications include low-cost low-power high-bandwidth switching of signals for broad-band services. A detailed description of the thyristor device, MMIC structure and design, and simulation and experimental results are presented. Multilayer laminate ball-grid-array package design for the switch matrix will also be explained in detail.