Defect mitigation of electronic devices is conventionally achieved using thermal annealing. To mobilize the defects very high temperature is necessary. Since thermal diffusion is random in nature, the process may take a prolonged period of time. In contrast, we demonstrate a room temperature annealing technique that takes only a few seconds. The fundamental mechanism is defect mobilization by atomic scale mechanical force originated from very high current density but low duty cycle electrical pulses. The high energy electrons lose their momentum upon collision with defects, yet low duty cycle suppresses any heat accumulation to keep the temperature at ambient. For 7×105 A/cm2 pulsed current, we report approximately 26% reduction in specific on-resistance, 50% increase of rectification ratio with lower ideality factor and reverse leakage current for as-fabricated vertical geometry GaN p-n diodes. We characterized microscopic defect density of the devices before and after the room temperature processing to explain the improvement in the electrical characteristics. Raman analysis reveals improvement in crystallinity of the GaN layer and approximately 40% relaxation of any post-fabrication residual strain compared to the as-received sample. Cross-sectional transmission electron microscopy (TEM) images and geometric phase analysis (GPA) results of high-resolution TEM (HRTEM) images further confirm the effectiveness of the proposed room temperature annealing technique to mitigate defects in the device. No detrimental effect, such as diffusion and/or segregation of elements, is observed as a result of applying high density pulsed current, as confirmed by energy dispersive X-ray spectroscopy (EDX) mapping.
β-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of β-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of β-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted β-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic β-phase to the defective cubic spinel γ-phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the γ-Al2O3, which has the same space group as β-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 ⟨110⟩ type in cubic structure. We show that post-implantation annealing at 1100 °C under the N2 atmosphere effectively recovers the β-phase; however, nano-sized voids retained within the β-phase structure and a γ-phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of β-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability.
more » « less- Award ID(s):
- 1856662
- NSF-PAR ID:
- 10439999
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 121
- Issue:
- 7
- ISSN:
- 0003-6951
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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