Its most commercially significant role is as the barrier layer in AlGaN/GaN heterostructures. The spontaneous and piezoelectric polarisation mismatch between AlGaN and GaN at the interface induces a two-dimensional electron gas (2DEG) in the GaN channel without doping — this is the active region of every GaN HEMT power device and RF transistor (see Gallium Nitride). The Al composition (typically 15–30%) and barrier thickness control the 2DEG charge density and thus device on-resistance and breakdown voltage.
As a standalone emitter material, high-Al-content AlGaN (x > 0.4) enables deep-UV LEDs for water purification, surface sterilisation (hospital environments, point-of-use water treatment), and fluorescence-based biosensing. This is the primary application differentiated from InGaN’s visible-light LEDs (see Indium Gallium Nitride). AlGaN photodetectors are also “solar-blind” (insensitive to visible solar background) — valued in UV sensing for flame detection and atmospheric monitoring.
AlGaN layers are grown by MOCVD on AlN or sapphire templates. High-Al-content growth faces challenges in cracking (thermal expansion mismatch) and threading dislocation density, limiting efficiency; this is the central manufacturing barrier for deep-UV LEDs.
Frontier
- Can AlGaN-based deep-UV LEDs (230–280 nm) reach >10% wall-plug efficiency at commercially viable power levels to displace mercury lamps in sterilisation?
- Does the AlGaN/GaN 2DEG interface quality set an exploitable ceiling on GaN power device switching speed, and can interface engineering push past it?
- Will high-Al-content AlGaN (>70% Al) prove manufacturable enough to enable solar-blind UV photodetectors at scale for defence and environmental sensing?