Investigating the bistability characteristics of GaN/AlN resonant tunneling diodes for ultrafast nonvolatile memory

• Published in: Japanese Journal of Applied Physics Vol. 54; no. 3; pp. 34201 - 1-034201-8
• Main Authors: Nagase, Masanori, Takahashi, Tokio, Shimizu, Mitsuaki
• Format: Journal Article
• Language: English
• Published: The Japan Society of Applied Physics 01.03.2015
• Subjects: Aluminum nitride; Bistability; Crystal defects; Degradation; Diodes; Electric potential; Gallium nitrides; Resonant tunneling
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.54.034201

The bistability characteristics of GaN/AlN resonant tunneling diodes (RTDs) grown on a sapphire substrate by metalorganic vapor phase epitaxy (MOVPE) were investigated to better understand their physical origin and explore their use in nonvolatile memories. The bistability current-voltage (I-V) characteristics of GaN/AlN RTDs, which were due to intersubband transitions and electron accumulation in the quantum well, were clearly observed over a wide temperature range between 50 and 300 K. However, the I-V characteristics sometimes degraded at temperatures above 250 K. Complex staircase structures were observed in the voltage region showing a negative differential resistance in the I-V curve, and the forward current increased or decreased rapidly as the forward-bias voltage increased. Repeated measurements of the I-V characteristics over the wide temperature range between 50 and 300 K revealed that the bistability characteristics of GaN/AlN RTDs degraded owing to the leakage of electrons accumulating in the quantum well through a deep level in the AlN barrier associated with crystal defects such as dislocations and impurities. Therefore, reduction in crystal defect and impurity densities in the AlN barrier, and a careful design that considers deep levels are important for realizing realize ultrafast nonvolatile memories based on the bistability characteristics of GaN/AlN RTDs.