Effects of substrate quality and orientation on the characteristics of III-nitride resonant tunneling diodes

Abstract

Al(Ga)N/GaN resonant tunneling diodes (RTDs) are grown by metal-organic chemical vapor deposition. The effects of material quality on room temperature negative differential resistance (NDR) behaviour of RTDs are investigated by growing the RTD structure on AlN, GaN, and lateral epitaxial overgrowth GaN templates. This reveals that NDR characteristics of RTDs are very sensitive to material quality (such as surface roughness and dislocations density). The effects of the aluminum content of AlGaN double barriers (DB) and polarization fields on NDR characteristic of AlGaN/GaN RTDs were also investigated by employing low dislocation density c-plane (polar) and m-plane (nonpolar) freestanding GaN substrates. Lower aluminum content in the DB RTD active layer and minimization of dislocations and polarization fields enabled a more reliable and reproducible NDR behaviour at room temperature.

Highly repeatable room temperature negative differential resistance in AlN/GaN resonant tunneling diodes grown by molecular beam epitaxy

“…This kind of feature can be utilized in a vast number of applications ranging from self-oscillators to logic and memory. 2 III-nitride RTDs [3][4][5][6][7][8][9][10][11][12][13][14] have attracted a great deal of interest in recent years as they have potential to increase the power output and operating temperature of RTDs due to the large band offsets available in pseudomorphic and III-nitride heterojunctions ($2 eV for AlN/GaN). Subsequently, intraband tunneling could enable a new class of tunneling injection devices.…”

“…There has been some success using non-polar GaN substrates 5,9 to circumvent polarization issues, as well as low temperature and pulsed NDR repeatability on polar substrates. 10 But to date, there are no reports of room-temperature NDR from devices grown on polar substrates which is simultaneously free from hysteresis, highly repeatable, and robust over multiple voltage sweeps.…”

“…10 But to date, there are no reports of room-temperature NDR from devices grown on polar substrates which is simultaneously free from hysteresis, highly repeatable, and robust over multiple voltage sweeps. Past researchers have attributed this lack of reproducibility to three main factors: (i) spontaneous and piezoelectric polarization along the c-axis leading to strong internal fields, [3][4][5] (ii) trapping effects, [5][6][7][8]21 and (iii) scattering and leakage pathways related to dislocations. 7 Some have even suggested that there may exist a percolation based leakage in barriers made from nitride ternary alloys.…”

Temperature dependence of the dark current and activation energy at avalanche onset of a GaN avalanche photodiodes

“…On top of this a low temperature GaN buffer and a thin GaN template layer were grown. Due to the 16% effective lattice mismatch between the sapphire substrate GaN, threading dislocation densities in this template at on the order of 10 9 cm −2 , see Refs (12,13). The rest of the device consists of a basic p-i-n device constructed by controlling the doping of the GaN.…”

Negative differential resistance characteristics of GaN-based resonant tunneling diodes with quaternary AlInGaN as barrier

“…As the representative material of third-generation semiconductors, GaN has developed rapidly in the past 20 years owing to its excellent material properties, such as wide band gap, high electron saturation velocity, and breakdown electric field. Compared with GaAs-based RTDs, theoretical estimations show that the output power of GaN-based RTDs could reach milliwatt or even watt levels at high operating frequency [3,4]. GaN-based AlGaN/GaN or AlN/GaN RTDs of DBS structure are the most widespread due to the high-quality materials that can be obtained.…”