F. Recht

Nonalloyed ohmic contacts in AlGaN/GaN HEMTs by ion implantation with reduced activation annealing temperature

This letter reports AlGaN/GaN high-electron mobility transistors with capless activation annealing of implanted Si for nonalloyed ohmic contacts. Source and drain areas were implanted with an Si dose of 1/spl times/10/sup 16/ cm/sup -2/ and were activated at /spl sim/1260/spl deg/C in a metal-organic chemical vapor deposition system in ammonia and nitrogen at atmospheric pressure. Nonalloyed ohmic contacts to ion-implanted devices showed a contact resistance of 0.96 /spl Omega//spl middot/mm to the channel. An output power density of 5 W/mm was measured at 4 GHz, with 58% power-added efficiency and a gain of 11.7 dB at a drain bias of 30 V.

Direct comparison of traps in InAlN/GaN and AlGaN/GaN high electron mobility transistors using constant drain current deep level transient spectroscopy

Traps in InAlN/GaN and AlGaN/GaN high electron mobility transistors (HEMTs) are identified and compared using constant drain-current deep level transient spectroscopy (CID-DLTS). For both structures with different barrier materials, the same drain-access electron trap at EC−0.57 eV dominates the drain-controlled CID-DLTS trap spectrum. This suggests that the physical source of this trap, previously associated with drain-lag, is not present in the barrier but instead is likely to reside in the GaN-buffer. Gate-controlled CID-DLS measurements, which are preferentially sensitive to the barrier under the gate, reveal different trap spectra for the two HEMTs, showing that choice of barrier materials can influence under-gate trap signatures.

Power Performance of AlGaN/GaN HEMTs Grown on SiC by Ammonia-MBE at 4 and 10 GHz

In this letter, we report on the microwave power and efficiency performance of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by ammonia molecular beam epitaxy (ammonia-MBE) on SiC substrates. At 4 GHz, an output power density of 11.1 W/mm with an associated power-added efficiency (PAE) of 63% was measured at V ds = 48 V on passivated devices. At 10 GHz, an output power density of 11.2 W/mm with a PAE of 58% was achieved for V ds = 48 V. These results are the highest reported power performance for AlGaN/GaN HEMTs grown by ammonia-MBE and the first reported for ammonia-MBE on SiC substrates.

Improved Performance of Plasma-Assisted Molecular Beam Epitaxy Grown AlGaN/GaN High Electron Mobility Transistors with Gate-Recess and CF4-Treatment

High performance AlGaN/GaN high electron mobility transistors grown by plasma-assisted molecular beam epitaxy were fabricated. An integrated slant field-plate was used to suppress the DC-RF dispersion and enhance the breakdown. A recessed-gate structure was adopted to increase the cutoff frequency from 17.5 to 22 GHz. And a CF4-plasma treatment prior to gate metallization was found effective in reducing the gate leakage by one order of magnitude and improving the stability of the RF power operation. Treatment in a mixture of HF and HNO3 acid was essential to ensure the effectiveness of the CF4-plasma treatment. Combination of these technologies yielded state-of-the-art MBE grown AlGaN/GaN HEMTs with stable high-power and high-efficiency operation. At 4-GHz frequency and 48-V bias, a CW power of 12 W/mm with 64% associated efficiency was achieved.

AlGaN/GaN HEMTs with Large Angle Implanted Nonalloyed Ohmic Contacts

In this work we report AIGaN/GaN HEMTs with nonalloyed ohmic contacts by large angle ion implantation with a contact resistance to the channel of 0.2 Omegamm.

AlGaN/GaNHEMT with High PAE and Breakdown Voltage Grown by Ammonia MBE

In this paper, a report on high PAE, high breakdown-voltage HEMTs grown by ammonia MBE is discussed. First, an AlN nucleation layer was grown by plasma-assisted MBE on SiC. Then GaN buffer was grown by ammonia MBE, followed by 30 nm ammonia Al_0.3Ga_0.7N. A sheet charge of 1x10¹³ cm^-2 with a mobility of 1500 cm²V^-1s^-1 was obtained from Hall measurements.