We have demonstrated an extremely low voltage rectifier by using p-GaN gate AlGaN/GaN high electron mobility transistors. In contrast to conventional GaN rectifiers, the turn-on voltage and on-state current can be decoupled, resulting in low turn-on voltage of 0.05 V and high on-state current achieved simultaneously with p-GaN designs. Furthermore, the role of p-GaN layer on current–voltage characteristics of p-GaN gated anode diode was investigated, indicating the p-GaN layer is the source of hole current. Combined the electron current with hole current, the total current was enhanced significantly with the ohmic p-GaN gate electrode. Finally, full-wave AC to DC rectification was demonstrated by a monolithically-integrated diode bridge rectifier with four p-GaN gated anode diodes. The bridge rectifier is able to operate at an input signal as low as 0.18 V, which is very promising for future power conversion applications.
High breakdown voltage (BV) AlGaAs/GaAs/AlGaAs diodes with a pair of hole and electron channels were studied taking account of the residual carbon impurity. The residual acceptor that would affect the charge balance was evaluated by separate growth. Utilizing the residual concentration, the acceptor concentrations (N
A) were examined with a fixed donor concentration of 1.1 × 1012 cm−2. For N
A of 0.9 × 1012 cm−2, the diode with 113 μm drift region length derived the highest BV of 1800 V. Temperature-dependent I–V measurements revealed the breakdown due to an avalanche multiplication. This implies a uniform electric field across the channels. Then, depletion of both channels was characterized by C–V measurements for obtaining capacitance shut-off voltages of the diodes. The lowest shut-off voltage was obtained for the 0.9 × 1012 cm−2
N
A diode. This would be due to the simultaneous depletion of hole and electron channels, i.e. the identical net concentration for acceptor and donor.
We studied the characteristics of deep-level traps in p-type HgCdTe diodes using the Deep Level Transient Fourier Spectroscopy (DLTFS) method. For both holes and electrons, two types of traps were observed. The DLTFS signal intensity of one type of trap increased with the carrier density in the HgCdTe, while the other did not exhibit a monotonic increase. While measuring the stability of these traps during cooling cycles, the DLTFS signal intensity of the first group was almost constant while that of the latter fluctuated with every cooling cycle. Stable traps originated from Hg vacancies, unstable traps are attributed to vacancy-impurity complex defects.
We studied the characteristics of deep-level traps in p-type HgCdTe diodes using the Deep Level Transient Fourier Spectroscopy (DLTFS) method. For both holes and electrons, two types of traps were observed. The DLTFS signal intensity of one type of trap increased with the carrier density in the HgCdTe, while the other did not exhibit a monotonic increase. While measuring the stability of these traps during cooling cycles, the DLTFS signal intensity of the first group was almost constant while that of the latter fluctuated with every cooling cycle. Stable traps originated from Hg vacancies, unstable traps are attributed to vacancy-impurity complex defects.
Breakdown voltage enhancement was studied for p-GaN/AlGaN/GaN heterostructure diodes, where residual Si donors during growth were compensated with Mg acceptors doped in the p-GaN layer. As decreasing of the p-GaN layer thicknesses (Tp-GaN) from 140 nm, breakdown voltages were increased, and maximized at 20 nm, then decreased at 0 nm. And, breakdown voltages of the 20 nm Tp-GaN diodes improved with increase of the drift region lengths. This is because a uniform electric field was obtained by compensation of the residual Si donors with the Mg acceptors. In addition, for a thicker p-GaN layer, the effects of the surface states were suppressed, and injection of a large number of holes under forward bias was observed. Consequently, the thick p-GaN layer is expected to enhance forward current. Adopting the results, potential of low on-resistance and high current for p-GaN gated anode diodes was demonstrated.
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