Abstract
AlGaN/GaN quantum structure is an excellent candidate for high speed infrared detectors based on intersubband transitions. However, fabrication of AlGaN/GaN quantum well infrared detectors suffers from polarization-induced internal electric field, which greatly limits the carrier vertical transport. In this article, a step quantum well is proposed to attempt solving this problem, in which a novel spacer barrier layer is used to balance the internal electric field. As a result, a nearly flat band potential profile is obtained in the step barrier layers of the AlGaN/GaN step quantum wells and a bound-to-quasi-continuum (B-to-QC) type intersubband prototype device with detectable photocurrent at atmosphere window (3–5 μm) is achieved in such nitride semiconductors.
Highlights
III-nitrides are employed in a wide range of applications such as solid-state lighting, display, wireless communication, and so on[1,2,3]
We report our efforts on modifying the internal electric fields in the AlGaN/GaN multiple quantum structures for infrared detection at the 3–5 μ m atmosphere window
The core idea is to create a nearly flat band potential in the step barrier layers by using step-quantum-wells. Such a flat band potential is much favorable for photocurrent vertical transport through the quasi-continuum (QC) states formed above the step barrier energy, while it still maintains high crystalline quality grown along c-axis
Summary
III-nitrides are employed in a wide range of applications such as solid-state lighting, display, wireless communication, and so on[1,2,3]. For a single-chip monolithic dual-band UV- and infrared- photodetector, it is not hard to fabricate solar-blind UV detectors based on AlGaN p-i-n structure at the present time, the current difficulty lies in realizing high performance infrared detectors based on III-nitrides, in particular at the 3–5 μ m atmosphere window. This difficulty basically originates from two aspects, i.e. the poor crystalline quality and effect of polarization-induced internal electric field[11,12]. An AlGaN-based bound-to-quasi-continuum (B-to-QC) type photodetector with a photocurrent peak at 3.40 μ m is achieved at 5 K, in agreement with the photo-absorption measurement
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