We fabricate and characterize a GaAsSb/InGaAs backward diode (BWD) toward a realization of high sensitivity zero bias microwave rectification for RF wave energy harvest. Lattice-matched p-GaAsSb/n-InGaAs BWDs were fabricated and their current-voltage (I-V) characteristics and S-parameters up to 67 GHz were measured with respect to several sorts of mesa diameters in μm order. Our theoretical model and analysis are well fitted to the measured I-Vs on the basis of WKB approximation of the transmittance. It is confirmed that the interband tunneling due to the heterojunction is a dominant transport mechanism to exhibit the nonlinear I-V around zero bias regime unlike recombination or diffusion current components on p-n junction contribute in large current regime. An equivalent circuit model of the BWD is clarified by confirming theoretical fitting for frequency dependent admittance up to 67 GHz. From the circuit model, eliminating the parasitic inductance component, the frequency dependence of voltage sensitivity of the BWD rectifier is derived with respect to several size of mesa diameter. It quantitatively suggests an effectiveness of mesa size reduction to enhance the intrinsic matched voltage sensitivity with increasing junction resistance and keeping the magnitude of I-V curvature coefficient.

This paper investigates current-gain and high-frequency characteristics of double heterojunction bipolar transistors (DHBTs) with a uniform GaAsSb, compositionally graded GaAsSb, uniform InGaAsSb, or compositionally graded InGaAsSb base. DHBTs with a compositionally graded InGaAsSb base exhibit a high current gain of ∼75 and fT=504GHz. In order to boost fmax of DHBTs with a compositionally graded InGaAsSb base, a highly doped GaAsSb base contact layer is inserted. The fabricated DHBTs exhibit fT/fmax=513/637GHz and a breakdown voltage of 5.2V.

We report on continuous-wave optoelectronic terahertz (THz) measurements using low-temperature grown (LTG) GaAsSb as photomixer material. A broadband log-periodic antenna and a six interdigital finger photomixer with 1 µm gap is fabricated on LTG-GaAsSb for THz generation and detection. At 0.37 THz, the resonance frequency of the inner most antenna tooth, we obtained a power of 6.3 nW. A Golay cell was used as detector. The photocarrier lifetime of the material was determined to be 700 fs by pump-probe experiments with an optical wavelength close to the band gap of LTG-GaAsSb. The band gap was 1.0 eV, measured by wavelength dependent pump-probe measurements.

We report for the first time the design, process and characterization of InP-based micrometer emitter InGaAlAs/GaAsSb/InP Double HBTs (DHBTs) and their microwave performance. The layer structure not only allows the implementation of InP collector free of current blocking, but also enables small turn-on voltage and ballistic launching of electrons due to the positive conduction band discontinuity of emitter to base. The DHBT structure was grown on nominal (001) InP substrates using MBE. Solid Si and CBr4 gas were used for n-type and p-type doing respectively. Fabricated large DHBTs showed high DC gain (> 80), small turn-on voltage 0.62 V, almost zero offset voltage, and nearly ideal base and collector current characteristics (ideality factors 1.0 for both B-E and B-C junctions). Small DHBTs demonstrated VCEO > 8 V and stable operation at high current density exceeding 100 kA/cm2. Maximum fT of 57 GHz and maximum fmax of 66 GHz were achieved from 1 20 µm2 devices at similar bias condition: JC = 8.0 104 A/cm2 and VCE =3.5 V. The InGaAlAs/GaAsSb/InP DHBTs appear to be a very promising HBT solution having simultaneous excellent RF and DC performances.