High gain GaN/AlGaN heterojunction phototransistor

Abstract

A GaN/AlGaN heterojunction bipolar phototransistor with gain in excess of 105 was demonstrated. From 360 to 400 nm, an eight orders of magnitude drop in responsivity was achieved. The phototransistor features a rapid electrical quenching of persistent photoconductivity, and exhibits high dark impedance and no dc drift. By changing the frequency of the quenching cycles, the detection speed of the phototransistor can be adjusted to accommodate specific applications. These results represent an internal gain UV detector with significantly improved performance over GaN-based photoconductors.

Characteristics of back-illuminated visible–blind UV photodetector based on AlxGa1−xN p–i–n photodiodes

“…However, the low-doping efficiencies typically associated with Al x Ga 1Àx N layers having high aluminum content can limit the fabrication of heavily doped p-type and n-type layers [7,8]. Even though these difficulties exist, several groups have reported promising results for the development of UV photodetectors, including such devices as photoconductors [9,10], Schottky photovoltaic detectors [11][12][13], p-n and p-i-n photodetectors [3,14,15], metal-semiconductor-metal (MSM) photodetectors [2,16], avalanche photodiodes [17] and phototransistors [18]. Among these devices, p-i-n photodetector structures are especially attractive, because they are compact, consume less power, are rugged and reliable, and can easily be integrated with other electronic circuitry.…”

Microstructures of AlGaN/AlN/Si (111) Grown by Metalorganic Chemical Vapor Deposition

“…Due to its wide bandgap and its unique properties, AlGaN is a very promising material in high-power, high-frequency applications [1][2][3][4], especially working with GaN film [5,6]. In the absence of bulk substrates, the growth of AlGaN is carried out on sapphire, silicon carbide or silicon (Si) by metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).…”

Performance Evaluation of GaN/InGaN Heterojunction Phototransistors

“…In the past, phototransistors based on lower bandgap materials have been demonstrated for infrared detection and fiber-optic communications [6]. However, since photocurrent gains in phototransistors are essentially related to the epitaxial material quality of the constituent bipolar transistor structures, fewer developments in III-Nbased phototransistors were reported [7,8].In this paper, we report a top-illuminated InGaN/GaN heterojunction phototransistor (HPT) grown on sapphire substrates. The HPT layer structure consists of a 2.5-μm-thick unintentionally doped GaN buffer layer, followed by a 880-nm Si-doped n-GaN sub-collector layer (n=3×10 18 cm -3 ), a 320-nm n-GaN collector layer (n= 1×10 17 cm -3 ), a 30-nm In x Ga 1-x N (x= 0-0.03) graded collector layer, a 110-nm Mg-doped In 0.03 Ga 0.97 N base layer (p~ 1×10 18 cm -3 ), a 30-nm In x Ga 1-x N (x=0.03-0) graded emitter layer and a 120-nm Si-doped n-GaN cap layer (n= 1×10 19 cm -3 ).…”