T. Henderson

Temperature dependences of current gains in GaInP/GaAs and AlGaAs/GaAs heterojunction bipolar transistors

The temperature dependences of current gain are investigated for both GaInP/GaAs and AlGaAs/GaAs heterojunction bipolar transistors (HBTs). Measured results indicate that for GaInP/GaAs HBTs the current gain at collector current densities >0.1 A/cm/sup 2/ remains nearly constant, independent of the substrate temperature for AlGaAs/GaAs HBTs. These current gain characteristics are examined, and the origin of the difference is attributed to the difference of the valence-band discontinuities in the base-emitter heterojunctions of the two HBTs. >

Microwave performance of a self-aligned GaInP/GaAs heterojunction bipolar transistor

The microwave performance of a self-aligned GaInP/GaAs heterojunction bipolar transistor (HBT) is presented. At an operating current density of 2.08*10/sup 4/ A/cm/sup 2/, the measured cutoff frequency is 50 GHz and the maximum oscillation frequency extrapolated from measured unilateral gain and the maximum available gain are 116 and 81 GHz, respectively, all using 20-dB/decade slopes. These results are compared with other reported high-frequency performances of GaInP HBTs. In addition, these results are compared with AlGaAs/GaAs HBTs having a similar device structure.<<ETX>>

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.

Model for degradation of GaAs/AlGaAs HBTs under temperature and current stress

The similarities between GaAs/AlGaAs heterojunction bipolar transistors (HBTs) and GaAs-based light-emitting diodes (LEDs) and laser diodes (LDs) under current and temperature stress are demonstrated. Electroluminescence on HBTs with degraded current gain shows a marked decrease in light emission. One device which suffered rapid degradation in current gain also showed a <110> dark line defect (DLD). Finally, an equation used to model light output as a function of time under bias stress in LEDs and LDs was modified to model collector current vs. time for HBTs under bias stress. An excellent fit to the data is shown.

Characterization of bias-stressed carbon-doped GaAs/AlGaAs power heterojunction bipolar transistors

We report on the performance of carbon-doped heterojunction bipolar transistors (HBTs) bias stressed at elevated temperatures. We have determined that in devices without a thin passivating layer of AlGaAs covering the extrinsic base, a tunneling-recombination current that increases in magnitude with the duration of the stress is generated. This current is seen in both the collector and the base at cryogenic temperatures. The variation of this current with temperature is primarily due to carrier freeze-out in the AlGaAs emitter. We hypothesize that this conduction mechanism is related to the generation of midgap traps in the base layer as a result of electron-hole recombination events.<<ETX>>

Extrinsic base surface passivation in GaInP/GaAs heterojunction bipolar transistors

The authors demonstrate excellent passivation of the extrinsic base surfaces in GaInP/GaAs heterojunction bipolar transistors (HBTs) having small emitter areas. Passivated devices with an area as small as 4*20 mu m/sup 2/ exhibit the highest reported current gain value of 2690 for GaInP/GaAs HBTs, while unpassivated 4*20- mu m/sup 2/ devices exhibit a current gain of only 500. Measured current gains as a function of collector current density are almost identical for devices with varying emitter widths of 4, 6, 8, 12, 16, and 100 mu m. The current gains are also nearly identical for devices with varying passivation ledge widths of 1, 2, 3, and 6 mu m. These results are contrasted with those of a previously published study reporting surface passivation for a GaInP/GaAs HBT with a large emitter area.<<ETX>>

High-efficiency X-band HBT power amplifier

We report on the state-of-the-art performance of monolithic HBT amplifiers at X-band. Single-chip, two-stage amplifiers have been designed and fabricated using AlGaAs/GaAs HBT process. An output power level of 12.5 W, with 51% power-added efficiency and 13 dB associated gain have been achieved at 8.5 GHz. The amplifier delivers more than 10 W output power with minimum 41% PAE in the 8.3-9.5 GHz band, and 9 W power with minimum 38% PAE in the 8.3-10.0 GHz band. The amplifier measures 4.5/spl times/4.5 mm/sup 2/ in size and is thermally ballasted for reliable operation. To our knowledge, these results represent state-of-the-art performance in terms of the combination of power, bandwidth, and efficiency for any monolithic solid-state amplifier technology.<<ETX>>

High-speed InGaP/GaAs HBTs using a simple collector undercut technique to reduce base-collector capacitance

High-speed InGaP/GaAs HBTs were fabricated using a simple collector undercut (CU) technique to physically remove the collector material underneath the extrinsic base region by selective etching for reducing base-collector capacitance (C/sub BC/). The best HBTs achieved a f/sub T/ of 80 GHz and a f/sub max/ (MSG/MAG) of 171 GHz. To our knowledge, this is the highest f/sub max/ (MSG/MAG) ever reported for the InGaP/GaAs HBTs. Compared to the HBTs without CUs, the CU HBTs showed a factor of 1.38 times improvement in the highest achievable f/sub max/ (MSG/MAG) due to the significant reduction of the C/sub BC/.

Hydrogen-related burn-in in GaAs/AlGaAs HBTs and implications for reliability

We report a burn-in effect in carbon-doped GaAs/AlGaAs HBTs that results in an increase in dc current gain. The burn-in is the result of the annihilation of hydrogen-related recombination centers due to electron injection into the base. This burn-in effect needs to be taken into account in long-term bias stress testing of HBTs. Unrealistic values of mean time to failure and activation energy may be calculated otherwise.

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 >