Semi-insulating C-doped GaN and high-mobility AlGaN/GaN heterostructures grown by ammonia molecular beam epitaxy

Abstract

A method of growing semi-insulating GaN epilayers by ammonia molecular beam epitaxy through intentional doping with carbon is reported. Thick GaN layers of high resistivity are an important element in GaN-based heterostructure field-effect transistors. A methane ion source was used as the carbon dopant source. The cracking of the methane gas by the ion source was found to be the key to the effective incorporation of carbon. High-quality C-doped GaN layers with resistivities greater than 106 Ω cm have been grown with high reproducibility and reliability. AlGaN/GaN heterostructures grown on the C-doped semi-insulating GaN-based layers exhibited a high-mobility two-dimensional electron gas at the heterointerface, with room-temperature mobilities typically between 1000 and 1200 cm2/V s, and liquid-nitrogen-temperature mobilities up to 5660 cm2/V s. The carrier density was almost constant, with less than 3% change over the measured temperature range.

Conductivity and Hall-effect in highly resistive GaN layers

“…1 Another possibility to obtain high resistive GaN layers is by acceptor doping. MBE grown C-doped layers 2 and hydride vapor phse epitaxial Zn-doped layers 3 with resistivity of 10 6 and 10 12 ⍀ cm, respectively, have been reported. Unfortunately, carrier concentration and mobility data on samples with resistivity higher than 14 ⍀ cm are not present in the literature due to the use of conductive substrates, 3 or unmeasurable Hall coefficients.…”

“…High resolution x-ray diffraction measurements showed a reasonable layer quality with Х7 arc min full width at half maximum of the ͑0002͒ scan. 9 Samples of about 6ϫ6 mm 2 were cut from each wafer and In contacts were alloyed at 850°C after appropriate surface cleaning. The ohmic behavior of the contacts was confirmed by current-voltage characteristics.…”

Interface structure and adhesion of wafer-bonded GaN/GaN and GaN/AlGaN semiconductors

“…A modulation-doped field-effect transistor based on the Al x Ga 1Ϫx N/GaN heterostructures has shown encouraging high-frequency, high-power, and high-temperature performance. 5 One of the major challenges in group III nitride semiconductors is the heterogeneous integration of free standing GaN-based devices with dissimilar substrates. [3][4][5][6] Direct wafer bonding has been reported to be an ideal approach to integrate mismatched materials and has been used to fabricate a number of advanced microelectronic or photonic devices.…”

“…5 One of the major challenges in group III nitride semiconductors is the heterogeneous integration of free standing GaN-based devices with dissimilar substrates. [3][4][5][6] Direct wafer bonding has been reported to be an ideal approach to integrate mismatched materials and has been used to fabricate a number of advanced microelectronic or photonic devices. 3,4,6,7 Wafer bonding of GaN and other related semiconductors has been reported by a few research groups, such as GaN/GaAs, 3,4 GaN/InP, 6 and GaN/GaN.…”

Impact of buffer charge on the reliability of carbon doped AlGaN/GaN-on-Si HEMTs

“…These deep levels are a necessary requirement for device operation since they suppress buffer leakage and short-channel effects [11]. RF devices frequently make use of Fe doping to render the GaN insulating [12] - [14], but for the higher voltages required for many power switching applications, it has been found that carbon doping delivers higher breakdown voltage and lower off-state leakage [15,16]. Unfortunately, it has also been found that using carbon can often result in significant current-collapse [10,15].…”