Barry Wu

In the semiconductor RF world, indium phosphide (InP) heterojunction bipolar transistors (HBTs) have historically been a niche technology. High substrate costs and a lack of manufacturing expertise have contributed to limited adoption throughout the electronics industry. InP is, however, an ideal technology for many high speed electronic applications. With superior peak electron velocity compared to Si and GaAs and a higher breakdown voltage than SiGe, InP has the potential to benefit many… Show more

In the semiconductor RF world, indium phosphide (InP) heterojunction bipolar transistors (HBTs) have historically been a niche technology. High substrate costs and a lack of manufacturing expertise have contributed to limited adoption throughout the electronics industry. InP is, however, an ideal technology for many high speed electronic applications. With superior peak electron velocity compared to Si and GaAs and a higher breakdown voltage than SiGe, InP has the potential to benefit many microwave, mmWave and even terahertz (THz) applications. It has been used successfully in the electronic design, emulation and test industry for nearly two decades, enabling some of the highest performing instruments, including a 110 GHz real-time oscilloscope. Increasingly, InP HBTs are used or being considered for next-generation aerospace and defense, automotive and 5G/6G platforms. Capitalizing on the benefits of InP HBTs will require advanced packaging techniques to maintain high frequency performance and an industry-wide effort to reduce substrate prices. Show less

A low-temperature GaAsSb extrinsic base regrowth process using in-situ hydrogen plasma treatment and MBE regrowth of a highly doped p+ GaAs1-ySby:C layer is developed on Keysight’s commercial GaAsSb/InP NpN DHBT technology platform. The SIMS data shows that the regrowth interface oxygen sheet concentration is effectively reduced by in-situ hydrogen plasma, and a 30% reduction of base resistance (Rb) of a standard emitter width GaAsSb/InP DHBT is demonstrated.

InAs/GaSb heterojunction Esaki diodes with a high peak current density of 9 MA/cm 2 are demonstrated. Negative differential resistance (NDR) is achieved from 300 to 4 K, showing that band-to-band tunneling (BTBT) is the dominant transport mechanism. By increasing the doping concentrations, the peak current increases because of more carriers available for tunneling. NDR is also clearly observed for the devices with nondegenerate doping concentrations, which could be attributed to the induced… Show more

InAs/GaSb heterojunction Esaki diodes with a high peak current density of 9 MA/cm 2 are demonstrated. Negative differential resistance (NDR) is achieved from 300 to 4 K, showing that band-to-band tunneling (BTBT) is the dominant transport mechanism. By increasing the doping concentrations, the peak current increases because of more carriers available for tunneling. NDR is also clearly observed for the devices with nondegenerate doping concentrations, which could be attributed to the induced quantum wells at the InAs/GaSb heterojunction. To calibrate the BTBT current, devices of different mesa areas were characterized. The peak current density increases as the device is scaled down. A model of tunneling enhancement close to the mesa sidewalls by the surface defects is proposed. TCAD simulations show that the electric fields close to the sidewalls are enhanced because of the induced surface defects by dry etching in InAs and GaSb. Careful processing steps to reduce those surface defects during etching steps are required to avoid an overestimation of the BTBT current. Show less

We demonstrate a type-II GaAsSb/InP source-terminated MMIC UTC photoreceiver delivering 0.15 A/W responsivity with 5.1 dBm RF power measured at 170 GHz. The photodiode-based MMIC demonstrated a small-signal 3-dB bandwidth of 220 GHz. The photodiode MMICs were subsequently mounted on sapphire and packaged.

Measurements are presented showing an extraction of base transit time and minority carrier electron mobility in GaAsSb-Base Indium-Phosphide Double Heterojunction Bipolar Transistors. For p-doped GaAsSb with doping value 6E19 cm-3, the electron diffusion constant was found to be 61 cm2/sec. The junction temperature Tj was also characterized at the bias point IC = 6 mA, VCB = 0.55V and determined to be 85o C, which corresponds to an electron mobility of 1970 cm2/(V-s).

A Type-II GaAsSb DHBT with an AlInP Emitter, doping-graded GaAsSb base and InP collector has been grown by molecular beam epitaxy. 0.38 m emitter devices have been fabricated by a triple-mesa wet etch process and demonstrated fT/fMAX = 470/540 GHz at JC = 5.1 mA/μm2 and VCB = 0.65 V. This performance is comparable to composition-graded base devices with similar emitter width.

Compositional graded base Al x Ga 1-x AsSb/InP DHBT is demonstrated to show DC current gain of ~100 with 300 Aring base and base sheet resistance of 1000 Omega/square. The improvement is more than 50% compared to uniform base GaAsSb/InP DHBT with the same base thickness and sheet resistance.

Type-II GaAsSb/InP double-HBTs (DHBTs) with a 20 nm base and 60 nm collector exhibit record transistor performance with f T = 670 GHz and off-state collector-emitter breakdown voltage of 3.2 V. Similar devices with a 30 nm base and 100 nm collector achieve simultaneous fi = 480 GHz and f MAX = 420 GHZ with 4.3 V breakdown voltage.