Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor seems the most promising. This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems.

AlGaN/GaN HEMTs-an overview of device operation and applications

The rapid development of the RF power electronics requires the introduction of wide bandgap material due to its potential in high output power density, high operation voltage and high input impedance GaN-based RF power devices have made substantial progresses in the last decade This paper attempts to review the latest developments of the GaN HEMT technologies, including material growth, processing technologies, device epitaxial structures and MMIC designs, to achieve the state-of-the-art microwave and millimeter-wave performance The reliability and manufacturing challenges are also discussed

GaN-Based RF Power Devices and Amplifiers

GaN high-electron-mobility-transistors (HEMTs) on SiC were fabricated with field plates of various dimensions for optimum performance Great enhancement in radio frequency (RF) current-voltage swings was achieved with acceptable compromise in gain, through both reduction in the trapping effect and increase in breakdown voltages When biased at 120 V, a continuous wave output power density of 322 W/mm and power-added efficiency (PAE) of 548% at 4 GHz were obtained using devices with dimensions of 055/spl times/246 /spl mu/m/sup 2/ and a field-plate length of 11 /spl mu/m Devices with a shorter field plate of 09 /spl mu/m also generated 306 W/mm with 496% PAE at 8 GHz Such ultrahigh power densities are a dramatic improvement over the 10-12 W/mm values attained by conventional gate GaN-based HEMTs

30-W/mm GaN HEMTs by field plate optimization

A zinc oxide (ZnO) field effect transistor exhibits large input amplitude by using a gate insulating layer. A channel layer and the gate insulating layer are sequentially laminated on a substrate. A gate electrode is formed on the gate insulating layer. A source contact and a drain contact are disposed at the both sides of the gate contact and are electrically connected to the channel layer via openings. The channel layer is formed from n-type ZnO. The gate insulating layer is made from aluminum nitride/aluminum gallium nitride (AlN/AlGaN) or magnesium zinc oxide (MgZnO), which exhibits excellent insulation characteristics, thus increasing the Schottky barrier and achieving large input amplitude. If the FET is operated in the enhancement mode, it is operable in a manner similar to a silicon metal oxide semiconductor field effect transistor (Si-MOS-type FET), resulting in the formation of an inversion layer.

High-electron mobility transistor with zinc oxide

Impurity-based p-type doping in wide-band-gap semiconductors is inefficient at room temperature for applications such as lasers because the positive-charge carriers (holes) have a large thermal activation energy. We demonstrate high-efficiency p-type doping by ionizing acceptor dopants using the built-in electronic polarization in bulk uniaxial semiconductor crystals. Because the mobile hole gases are field-ionized, they are robust to thermal freezeout effects and lead to major improvements in p-type electrical conductivity. The new doping technique results in improved optical emission efficiency in prototype ultraviolet light-emitting-diode structures. Polarization-induced doping provides an attractive solution to both p- and n-type doping problems in wide-band-gap semiconductors and offers an unconventional path for the development of solid-state deep-ultraviolet optoelectronic devices and wide-band-gap bipolar electronic devices of the future.

https://science.sciencemag.org/content/sci/327/5961/60.full.pdf

Polarization-Induced Hole Doping in Wide–Band-Gap Uniaxial Semiconductor Heterostructures

A group III nitride based high electron mobility transistor (HEMT) (10) is disclosed that provides improved high frequency performance. One embodiment of the HEMT (10) comprises a GaN buffer layer (26), with an AlyGa1-yN (y=1 or y 1) layer (28) on the Gan buffer layer (26). An AlxGa1-xN (0≤x≤0.5) barrier layer (30) is on the AlyGa1-yN layer (28), opposite the GaN buffer layer (26), the AlyGa1-yN layer (28) having a higher Al concentration than that of the AlxGa1-xN barrirer layer (30). A preferred AlyGa1-yN layer (28) has y=1 or y≃1 and a preferred AlxGa1-xN barrier layer (30) has 0≤0.5. A 2DEG (38) forms at the interface between the GaN buffer layer (26) and the AlyGa1-yN layer (28). Respective source, drain and gate contacts (32, 34, 36) are formed on the AlxGa1-xN barrier layer (30). The HEMT (10) can also include a substrate (22) adjacent to the buffer layer (26), opposite the AlyGa1-yN layer (28) and a nucleation layer (24) can be included between the GaN buffer layer (26) and the substrate (22).

Group-iii nitride based high electron mobility transistor (hemt) with barrier/spacer layer

We review our work in the area of large scale InP photonic integrated circuits (PIC). We will review dense wavelength division multiplexed (DWDM) transmitter and receiver PICs with up to 40 channels, and operating at data rates up to 40 Gbit/s.

Large-Scale Photonic Integrated Circuits

A single-chip 40-channel dense wavelength division multiplexed, monolithic, InP transmitter photonic integrated circuit capable of operating at per channel data rate of 40 Gbit/s for a combined data rate of 1.6 Tbit/s is demonstrated.

Single-chip 40-channel InP transmitter photonic integrated circuit capable of aggregate data rate of 1.6 Tbit/s

Large-signal behavior with a fixed load and varying supply voltages was proposed for characterizing the quality of AlGaN/GaN HEMTs. Improved devices demonstrated constantly high PAEs of 56-62% at 8 GHz throughout a wide voltage range from 10 to 40 V. These 300-/spl mu/m-wide devices also generated 3.1-W output power with only 3.4-dB gain compression at 45 V, which translates to 10.3-W/mm power density; the highest for any FET of the same size.

P. Chavarkar

Papers

30-W/mm GaN HEMTs by field plate optimization

Group-iii nitride based high electron mobility transistor (hemt) with barrier/spacer layer

Large-Scale Photonic Integrated Circuits

Single-chip 40-channel InP transmitter photonic integrated circuit capable of aggregate data rate of 1.6 Tbit/s

Bias-dependent performance of high-power AlGaN/GaN HEMTs