Huan Zhao

Bio: Huan Zhao is an academic researcher from Chalmers University of Technology. The author has contributed to research in topics: Molecular beam epitaxy & Quantum well. The author has an hindex of 10, co-authored 38 publications receiving 306 citations. Previous affiliations of Huan Zhao include Chinese Academy of Sciences.

1.55 mu m GaInNAs resonant-cavity-enhanced photodetector grown on GaAs

Abstract: We report the design, growth, fabrication, and characterization of a GaAs-based resonant-cavity-enhanced (RCE) GaInNAs photodetector operating at 1.55μm. The structure of the device was designed using a transfer-matrix method (TMM). By optimizing the molecular-beam epitaxy growth conditions, six GaInNAs quantum wells were used as the absorption layers. Twenty-five (25)- and 9-pair GaAs∕AlAs-distributed Bragg reflectors were grown as the bottom and top mirrors. At 1.55μm, a quantum efficiency of 33% with a full width at half maximum of 10nm was obtained. The dark current density was 3×10−7A∕cm2 at a bias of 0V and 4.3×10−5A∕cm2 at a reverse bias of 5V. The primary time response measurement shows that the device has a rise time of less than 800ps.

Development of a 557 GHz GaAs monolithic membrane-diode mixer

Abstract: We present the development of a monolithically integrated 557 GHz membrane Schottky diode mixer. RF test shows state-of-the-art performance with an optimum receiver noise temperature below 1300 K DSB and an estimated mixer DSB conversion loss of 9 dB and a mixer DSB noise temperature of 1100 K including all losses.

Anisotropic transport properties in InAs/AlSb heterostructures

Abstract: We have investigated the anisotropic transport behavior of InAs/AlSb heterostructures grown on a (001) InP substrate. An electrical analysis showed anisotropic sheet resistance Rsh and electron mobility μn in the two dimensional electron gas (2DEG). Hall measurements demonstrated an enhanced anisotropy in μn when cooled from room temperature to 2 K. High electron mobility transistors exhibited 27% higher maximum drain current IDS and 23% higher peak transconductance gm when oriented along the [1-10] direction. The anisotropic transport behavior in the 2DEG was correlated with an asymmetric dislocation pattern observed in the surface morphology and by cross-sectional microscopy analysis of the InAs/AlSb heterostructure.

Terahertz GaAs Schottky diode mixer and multiplier MIC's based on e-beam technology

Abstract: We present the progress of the technological development of a full e-beam based monolithically integrated Schottky diode process applicable for sub-millimetre wave multipliers and mixers. Evaluation of the process has been done in a number of demonstrators showing state-of-the-art performance, including various multiplier circuits up to 200 GHz with a measured flange efficiency of above 35%, as well as heterodyne receiver front-end modules operating at 340 GHz and 557 GHz with a measured receiver DSB noise temperature of below 700 K and 1300 K respectively.

A survey on terahertz communications

Abstract: With the exponential growth of the data traffic in wireless communication systems, terahertz (THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation (5G), bridging the gap between millimeter wave (mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency (IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.

THz Diode Technology: Status, Prospects, and Applications

Abstract: Found in many terahertz (THz) and submillimeter-wave systems, GaAs Schottky diodes continue to be one of the most useful THz devices. As a low-parasitic device that operates well into the THz range, Schottky diodes provide useful detection and power generation for a number of practical applications. Mixers and multipliers, working as high as ~3 THz, have already been demonstrated. This paper reviews the current status of diode technology, detailing some of the different ways for fabricating THz chips. An overview regarding the current state of technology and performance for THz frequency multipliers and mixers is presented, along with applications enabled by these diodes.

A multi-spectral and polarization-selective surface-plasmon resonant mid-infrared detector

Abstract: We demonstrate a multi-spectral polarization sensitive mid-infrared dots-in-a-well (DWELL) photodetector utilizing surface-plasmonic resonant elements, with tailorable frequency response and polarization selectivity. The resonant responsivity of the surface-plasmon detector shows an enhancement of up to 5 times that of an unpatterned control detector. As the plasmonic resonator involves only surface patterning of the top metal contact, this method is independent of light-absorbing material and can easily be integrated with current focal plane array processing for imaging applications.

A multispectral and polarization-selective surface-plasmon resonant midinfrared detector

Abstract: We demonstrate a multispectral polarization sensitive midinfrared dots-in-a-well photodetector utilizing surface-plasmonic resonant elements, with tailorable frequency response and polarization selectivity. The resonant responsivity of the surface-plasmon detector shows an enhancement of up to five times that of an unpatterned control detector. As the plasmonic resonator involves only surface patterning of the top metal contact, this method is independent of light-absorbing material and can easily be integrated with current focal plane array processing for imaging applications.

Semiconductor infrared plasmonics

Abstract: Abstract The coupling between light and collective oscillations of free carriers at metallic surfaces and nanostructures is at the origin of one of the main fields of nanophotonics: plasmonics. The potential applications offered by plasmonics range from biosensing to solar cell technologies and from nonlinear optics at the nanoscale to light harvesting and extraction in nanophotonic devices. Heavily doped semiconductors are particularly appealing for the infrared spectral window due to their compatibility with microelectronic technologies, which paves the way toward their integration in low-cost, mass-fabricated devices. In addition, their plasma frequency can be tuned chemically, optically, or electrically over a broad spectral range. This review covers the optical properties of the heavily doped conventional semiconductors such as Ge, Si, or III–V alloys and how they can be successfully employed in plasmonics. The modeling of their specific optical properties and the technological processes to realize nanoantennas, slits, or metasurfaces are presented. We also provide an overview of the applications of this young field of research, mainly focusing on biosensing and active devices, among the most recent developments in semiconductor plasmonics. Finally, an outlook of further research directions and the potential technological transfer is presented.