An official website of the United States government
Abstract We report on low resistivity (1.1 Ω cm) in p-type bulk doping of N-polar GaN grown by metalorganic chemical vapor deposition. High nitrogen chemical potential growth, facilitated by high process supersaturation, was instrumental in reducing the incorporation of compensating oxygen as well as nitrogen-vacancy-related point defects. This was confirmed by photoluminescence studies and temperature-dependent Hall effect measurements. The suppressed compensation led to an order of magnitude improvement in p-type conductivity with the room-temperature hole concentration and mobility measuring 6 × 10 17 cm −3 and 9 cm 2 V −1 s −1 , respectively. These results are paramount in the pathway towards N-polar GaN power and optoelectronic devices.
more »
« less
Systematic oxygen impurity reduction in smooth N-polar GaN by chemical potential control
Abstract Process chemical potential control and dislocation reduction were implemented to control oxygen concentration in N-polar GaN layers grown on sapphire substrates via metal organic chemical vapor deposition (MOCVD). As process supersaturation was changed from ∼30 to 3400, the formation energy of the oxygen point defect increased, which resulted in a 25-fold decrease in oxygen incorporation. Reducing dislocations by approximately a factor of 4 (to ∼10 9 cm −3 ) allowed for further reduction of oxygen incorporation to the low-10 17 cm −3 range. Smooth N-polar GaN layers with low oxygen content were achieved by a two-step process, whereas first a 1 µ m thick smooth N-polar layer with high oxygen concentration was grown, followed by low oxygen concentration layer grown at high supersaturation.
more »
« less
- PAR ID:
- 10318729
- Date Published:
- Journal Name:
- Semiconductor Science and Technology
- Volume:
- 37
- Issue:
- 1
- ISSN:
- 0268-1242
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We demonstrate controlled Si doping in the low doping range of 5 × 10 15 –2.5 × 10 16 cm −3 with mobility >1000 cm 2 V −1 s −1 in GaN films grown by metalorganic chemical vapor deposition. The carbon-related compensation and mobility collapse were prevented by controlling the electrochemical potential near the growth surface via chemical potential control (CPC) and defect quasi-Fermi level (dQFL) point-defect management techniques. While the CPC was targeted to reduce the net C N concentration, the dQFL control was used to reduce the fraction of C atoms with the compensating configuration, i.e. C N − 1 . The low compensating acceptor concentration was confirmed via temperature-dependent Hall effect analysis and capacitance–voltage measurements.more » « less
-
Record low resistivities of 10 and 30 Ω cm and room-temperature free hole concentrations as high as 3 × 10 18 cm −3 were achieved in bulk doping of Mg in Al 0.6 Ga 0.4 N films grown on AlN single crystalline wafer and sapphire. The highly conductive films exhibited a low ionization energy of 50 meV and impurity band conduction. Both high Mg concentration (>2 × 10 19 cm −3 ) and low compensation were required to achieve impurity band conduction and high p-type conductivity. The formation of V N -related compensators was actively suppressed by chemical potential control during the deposition process. This work overcomes previous limitations in p-type aluminum gallium nitride (p-AlGaN) and offers a technologically viable solution to high p-conductivity in AlGaN and AlN.more » « less
-
High room temperature n-type mobility, exceeding 300 cm 2 /Vs, was demonstrated in Si-doped AlN. Dislocations and C N −1 were identified as the main compensators for AlN grown on sapphire and AlN single crystalline substrates, respectively, limiting the lower doping limit and mobility. Once the dislocation density was reduced by the growth on AlN wafers, C-related compensation could be reduced by controlling the process supersaturation and Fermi level during growth. While the growth on sapphire substrates supported only high doping ([Si] > 5 × 10 18 cm −3 ) and low mobility (∼20 cm 2 /Vs), growth on AlN with proper compensation management enabled controlled doping at two orders of magnitude lower dopant concentrations. This work is of crucial technological importance because it enables the growth of drift layers for AlN-based power devices.more » « less
-
We report the electrical properties of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) structures with a Ga2O3 passivation layer grown by metal–organic chemical vapor deposition (MOCVD). In this study, three different thicknesses of β-Ga2O3 dielectric layers were grown on Al0.3Ga0.7N/GaN structures leading to metal-oxide-semiconductor-HFET or MOSHFET structures. X-ray diffraction (XRD) showed the (2¯01) orientation peaks of β-Ga2O3 in the device structure. The van der Pauw and Hall measurements yield the electron density of ~ 4 × 1018 cm−3 and mobility of ~770 cm2V−1s−1 in the 2-dimensional electron gas (2DEG) channel at room temperature. Capacitance–voltage (C-V) measurement for the on-state 2DEG density for the MOSHFET structure was found to be of the order of ~1.5 × 1013 cm−2. The thickness of the Ga2O3 layer was inversely related to the threshold voltage and the on-state capacitance. The interface charge density between the oxide and Al0.3Ga0.7N barrier layer was found to be of the order of ~1012 cm2eV−1. A significant reduction in leakage current from ~10−4 A/cm2 for HFET to ~10−6 A/cm2 for MOSHFET was observed well beyond pinch-off in the off-stage at -20 V applied gate voltage. The annealing at 900° C of the MOSHFET structures revealed that the Ga2O3 layer was thermally stable at high temperatures resulting in insignificant threshold voltage shifts for annealed samples with respect to as-deposited (unannealed) structures. Our results show that the MOCVD-gown Ga2O3 dielectric layers can be a strong candidate for stable high-power devices.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1088/1361-6641/ac3638
