Demonstration of a 77-GHz heterojunction bipolar transferredelectron device

We demonstrate for the first time a heterojunction bipolar transferred electron device (HBTED), a device with a bipolar transistor-like structure in which Gunn oscillations occur. The use of a graded doping profile in the collector region is, we believe, a key factor in the device design. AlGaAs/GaAs HBTEDs fabricated on semi-insulating GaAs substrates exhibit free-running oscillations at a frequency of around 77 GHz. The third (emitter) terminal enables this device to be injection-locked and to function as a self-oscillating mixer     

High-performance carbon-doped base GaAs/AlGaAs heterojunction bipolar transistor grown by MOCVD

High-performance HBTs with a carbon-doped base layer (p=4*10/sup 19/ cm/sup -3/) are reported. The use of carbon as a p-type dopant allows the emitter-base p-n junction to be accurately positioned relative to the heterojunction, and the MOCVD growth method ensures consistency and uniformity of the wafer epitaxial structure. Microwave HBTs with current gains h/sub FE/=50 and f/sub T/ and f/sub max/ values of 42 GHz and 117 GHz, respectively, are reported.<>     

Design and analysis of heterojunction bipolar transferred electrondevices

The design of the heterojunction bipolar transferred electron device (HBTED) is considered. MOCVD-grown AlGaAs/GaAs HBTEDs were fabricated and 60 GHz operation was confirmed by on-wafer measurements. Analysis of the device operation is aided by the use of Monte Carlo device simulations, equivalent circuit model simulations and two-dimensional (2-D) drift-diffusion model simulations and the simulation results are compared with measurements on the fabricated HBTEDs and HBTED test structures. The effects of the external base-collector region and current spreading in the collector region are investigated and the latter is found to be of great importance. Our simulations show that having an appropriately graded collector doping profile can compensate the current spreading and this hypothesis is supported by measurement results. Conclusions are drawn regarding the design of practical HBTEDs for mm-wave oscillator applications     

Self-heating effect compensation in HBTs and its analysis andsimulation

A simple technique, inserting a specified resistance in the bias circuit, to compensate self-heating effect in DC and pulse characteristics of HBTs is proposed and demonstrated. Utilizing the bias scheme dependence of HBT behaviors, the compensation is achieved due to the cancellation of the positive and negative thermal-electric feedback inside HBTs. An analytical expression relating the specified resistance with the physical parameters of HBT is presented. The accurate simulation of both the self-heating effect and its compensation is, for the first time, demonstrated with a modified Gummel-Poon model     

High reliability InGaP/GaAs HBT

Excellent long term reliability InGaP/GaAs heterojunction bipolar transistors (HBT) grown by metalorganic chemical vapor deposition (MOCVD) are demonstrated. There were no device failures (T=10000 h) in a sample lot of ten devices (L=6.4 μm ×20 μm) under moderate current densities and high-temperature testing (J_c=25 kA/cm ², V_ce=2.0 V, Junction Temp =264°C). The dc current gain for large area devices (L=75 μm ×75 μm) at 1 kA/cm² at a base sheet resistance of 240 ohms/sq (4×10 ¹⁹ cm^-3@700 Å) was over 100. The dc current gain before reliability testing (L=6.4 μm ×10 μm) at 0.8 kA/cm² was 62. The dc current gain (0.8 kA/cm²) decreased to 57 after 10000 h of reliability testing. The devices showed an f_T=61 GHz and f_max=103 GHz. The reliability results are the highest ever achieved for InGaP/GaAs HBT and these results indicate the great potential of InGaP/GaAs HBT for numerous low- and high-frequency microwave circuit applications. The reliability improvements are probably due to the initial low base current at low current densities which result from the low surface recombination of InGaP and the high valence band discontinuity between InGaP and GaAs