Edward A. Beam

A monolithic 4 bit 2 GSps resonant tunneling analog-to-digital converter

The combination of resonant-tunneling diodes and heterostructure field-effect transistors provides a versatile technology for implementing microwave digital and mixed-signal applications. Here we demonstrate and characterize the first monolithic flash analog-to-digital converter (ADC) in this technology. The first-pass ADC achieved 2.7 effective bits at 2 gigasamples per second (Gsps) for a 220-MHz input signal. The one-bit quantizer achieved a single-tone spurious free dynamic range greater than 40 dB at 2 Gsps for a 220-MHz single-tone input with dithering.

The use of tertiarybutylphosphine and tertiarybutylarsine for the metalorganic molecular beam epitaxy of the In0.53Ga0.47As/InP and In0.48Ga0.52P/GaAs materials systems

This paper describes a study on the use of thermally cracked tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBA) with elemental Ga and In sources for the metalorganic molecular beam epitaxy (MOMBE) growth of the In 0.53 Ga 0.47 As/InP and In 0.48 Ga 0.52 P/GaAs materials systems. Modulated beam mass spectroscopy was used to characterize the thermal decomposition of these Group-V metal alkyls. Results indicate that As 2 and P 2 are the dominant growth species produced when cracker temperatures greater than 700°C are used. These conditions result in high quality epitaxial layers with essentially zero oval defects (less than l/cm 2 ) despite the use of elemental Group-Ill sources. Results of doping and heterointerface studies indicate that these Group-V precursors are suitable replacements for hydride sources. Application of these precursors for device structure growth including heterojunction bipolar transistors (HBTs) and resonant tunneling diodes (RTDs) is also described.

Phonon mode study of near-lattice-matched InxGa1-xAs using micro-Raman spectroscopy

We identify the four allowable phonon modes in InxGa1−xAs on InP:InAs‐like transverse optical (TO) (225±2 cm−1), InAs‐like longitudinal optical (LO) (233±1 cm−1), GaAs‐like TO (255±2 cm−1), and GaAs‐like LO (269±1 cm−1), using the selectivity of first‐order Raman scattering off the (100) normal surface and the (011) cleaved plane and detailed line‐shape analysis employing a sequential simplex optimization procedure. Raman scattering off the (011) cleaved plane was achieved for the first time in thin‐film InGaAs using microprobing capabilities (∼1 μm). We also identify another phonon mode R* at 244 cm−1 which is attributed to an alloy disorder mode in these films. For the five identified phonon modes, a linear relationship between the Raman frequencies and composition determined from x‐ray diffraction was determined for near‐lattice‐matched conditions (0.42<1−x<0.52).

Current transport mechanism in GaInP/GaAs heterojunction bipolar transistors

GaInP/GaAs heterojunction bipolar transistors (HBTs) and both graded and abrupt AlGaAs/GaAs HBTs were fabricated. A total of 20 wafers were analyzed. Comparisons of the experimental results establish that the dominant carrier transport mechanism in GaInP/GaAs HBTs is the carrier diffusion through the base layer. This suggests that the conduction-band barrier across the GaInP/GaAs emitter-base junction is so small that the barrier spike does not affect the carrier transport. This result differs from other published results which, by studying device structures other than HBTs, determined the conduction band barrier to be as large as approximately 50% of the bandgap difference. The findings of the present investigation, however, agree well with another published work which also examined an HBT structure. The difference between these works is discussed. >

High-speed InP/InGaAs heterojunction bipolar transistors

Very-high-performance common-emitter InP/InGaAs single heterojunction bipolar transistors (HBTs) grown by metalorganic molecular beam epitaxy (MOMBE) are reported. They exhibit a maximum oscillation frequency (f/sub T/) of 180 GHz at a current density of 1*10/sup 5/ A/cm/sup 2/. this corresponds to an (R/sub B/C/sub BC/)/sub eff/=f/sub T//(8 pi f/sup 2//sub max/) delay time of 0.12 ps, which is the smallest value every reported for common-emitter InP/InGaAs HBTs. The devices have 11 mu m/sup 2/ total emitter area and exhibit current gain values up to 100 at zero base-collector bias voltage. The breakdown voltage of these devices is high with measured BV/sub CEO/ and BV/sub CEO/ of 8 and 17 V, respectively.<<ETX>>

Co-integrated resonant tunneling and heterojunction bipolar transistor full adder

We present the first resonant tunneling bipolar transistor integrated circuits operating at room temperature. The circuits are comprised of co-integrated resonant tunneling and double heterojunction bipolar transistors based on III-V heteroepitaxy on InP substrates. The resonant tunneling bipolar transistors exhibit a peak-to-valley collector current ratio exceeding 70 which is higher than previous room temperature reports. Using this technology we demonstrate a 3-transistor XNOR, a 6-transistor XOR, a 5-transistor CARRY, and a 17-transistor full adder, all using a 3 V supply.<<ETX>>

Co-integration of resonant tunneling and double heterojunction bipolar transistors on InP

The authors report the first co-integration of resonant tunneling and heterojunction bipolar transistors. Both transistors are produced from a single epitaxial growth by metalorganic molecular beam epitaxy, on InP substrates. The fabrication process yields 9- mu m/sup 2/-emitter resonant tunneling bipolar transistors (RTBTs) operating at room temperature with peak-to-valley current ratios (PVRs) in the common-emitter transistor configuration, exceeding 70, at a resonant peak current density of 10 kA/cm/sup 2/, and a differential current gain at resonance of 19. The breakdown voltage of the In/sub 0.53/Ga/sub 0.47/As-InP base/collector junction, V/sub CBO/, is 4.2 V, which is sufficient for logic function demonstrations. Co-integrated 9- mu m/sup 2/-emitter double heterojunction bipolar transistors (DHBTs) with low collector/emitter offset voltage, 200 mV, and DC current gain as high as 32 are also obtained. On-wafer S-parameter measurements of the current gain cutoff frequency (f/sub T/) and the maximum frequency of oscillation (f/sub max/) yielded f/sub T/ and f/sub max/ values of 11 and 21 GHz for the RTBT and 59 and 43 GHz for the HBT, respectively.<<ETX>>

In situ detection of relaxation in InGaAs/GaAs strained layer superlattices using laser light scattering

We report the use of laser light scattering (LLS) for the in situ detection of strained epitaxial layer relaxation. Strained layer superlattices (SLSs) of InGaAs/GaAs were prepared by molecular beam epitaxy. The rapid increase in the LLS signal was interpreted as increased surface roughness due to surface steps generated during InGaAs relaxation. The LLS signal was sharply peaked with respect to the azimuthal angle (the rotation angle between crystal axes and the detection axis), indicating the scattering comes primarily from α misfit dislocations which run parallel to the (011) direction. The growth time at which the LLS signal onset occurred, together with the InGaAs growth rate, yielded the critical layer thickness, hc. The hc value for SLSs of In0.17Ga0.83As/GaAs with thicknesses of 4.6/17 and 4.6/7.8 nm were 25 and 23 nm, respectively, and almost identical to values obtained for single InGaAs layers. The observed values of hc are greater than those calculated using the standard force‐balance model. ...

Observation of resonant tunneling at room temperature in GaInP/GaAs/GaInP double-heterojunction bipolar transistor

Negative differential resistance (NDR) has been observed at room temperature in GaInP/GaAs double-heterojunction bipolar transistors (DHBTs). Both the common-emitter and common-base current-voltage characteristics and their magnetic field dependence have been studied to confirm that the observed NDR is due to resonant tunneling. The collector-base voltages at which the collector current resonances occur are calculated and are consistent with the measured values. The devices exhibit an offset voltage of 57 mV and saturation voltage of >

Room-temperature operation of a resonant-tunneling hot-electron transistor based integrated circuit

The first resonant-tunneling hot-electron transistor (RHET) EXCLUSIVE-NOR integrated circuit that operates at room temperature is demonstrated. The XNOR circuit consisting of a single resonant-tunneling transistor and four thin-film resistors, exhibits a 500-mV output voltage swing between the high- and low-logic levels when biased with a 1.8-V supply. The transistor, which features a novel InGaP collector barrier, has a peak current density of 4*10/sup 4/ A-cm/sup -2/, a common-base transfer coefficient of 0.9, and a peak-to-valley current ratio of 10:1 when operated in a common-emitter mode.<<ETX>>