Abstract
Double barrier GaN/AlN resonant tunneling heterostructures have been grown by molecular beam epitaxy on the (0001) plane of commercially available bulk GaN substrates. Resonant tunneling diodes were fabricated; room temperature current-voltage measurements reveal the presence of a negative differential conductance region under forward bias with peak current densities of ~6.4 $kA/cm^2$ and a peak to valley current ratio of ~1.3. Reverse bias operation presents a characteristic turn-on threshold voltage intimately linked to the polarization fields present in the heterostructure. An analytic electrostatic model is developed to capture the unique features of polar-heterostructure-based resonant tunneling diodes; both the resonant and threshold voltages are derived as a function of the design parameters and polarization fields. Subsequent measurements confirm the repeatability of the negative conductance and demonstrate that III-nitride tunneling heterostructures are capable of robust resonant transport at room temperature.
Highlights
Resonant tunneling of electrons in III-V semiconductors has been extensively studied since Tsu and Esaki theoretically investigated tunneling transport across multibarrier heterostructures with periods comparable to the electron wavelength [1]
Despite the steady progress in output power and frequency of operation, resonant tunneling diodes (RTDs) oscillators are yet to be demonstrated at the milliwatt output power level for frequencies higher than 1 THz, which is required for most practical applications [5]
We systematically investigated the impact of the growth temperature on resonant tunneling transport in nitride RTDs; this experimental study will be published separately
Summary
Resonant tunneling of electrons in III-V semiconductors has been extensively studied since Tsu and Esaki theoretically investigated tunneling transport across multibarrier heterostructures with periods comparable to the electron wavelength [1]. It has been suggested that the high density of defects present in GaN films grown on sapphire (with a typical dislocation density of 109 cm−2) can act as electron traps, leading to selfcharging effects and preventing coherent transport of carriers It should be pointed out, that repeatable roomtemperature NDC was reported in a multiple quantum well heterostructure lattice matched to an AlN film grown on sapphire [24]. Room-temperature I-V measurements show a clear resonant peak and repeatable NDC under forward bias in each of the fabricated samples This repeatable operation measured across different device designs has helped uncover several unique features present in polar RTDs and demonstrate that III-nitride heterostructures are capable of robust resonant tunneling transport at room temperature
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