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Piezoelectric effect and spontaneous polarization in computer modelling of AIII--N heterostructures

Piasecki T., Kośnikowski W., Paszkiewicz B.

Optica Applicata

2005

Vol. 35, nr 3

597-604

The Ga, Al and In nitrides (AIII--N) are complete material system suitable in high power and high temperature electronic devices such as AlxGa1-xN/GaN heterostructure field effect transistor (HFET). The examples of computer modelling of AIII--N heterostructures were shown. AIII--N materials exhibit strong piezoelectric and spontaneous polarization. The computer modelling results showing the influence of layer polarity on carrier distribution in AlxGa1-xN/GaN heterostructure were shown. Only in Ga-faced heterostructures 2-dimensional electron gas (2DEG) is formed. The effect of AlxGa1-xN layer relaxation on 2DEG concentration in AlxGa1-xN/GaN heterostructure was examined. The difference in spontaneous polarization in AlxGa1-xN and GaN caused high 2DEG concentration even in AlxGa1-xN/GaN heterostructures with relaxed Alx-Ga1-xN layer. Polarization field in AlxGa1-xN layer in AlxGa1-xN/GaN heterostructure was enough for achieving high 2DEG concentrations in undoped heterostructure. Strained AlxGa1-xN layer was introduced into typical HFET heterostructure. GaN layer above an interlayer was depleted and the negative influence of using non semi-insulating GaN layer in HFET transistor was reduced.

Komputerowe modelowanie przyrządów opartych na heterostrukturze AIGaN/GaN/Al2O3

Pasecki T., Kośnikowski W.

Elektronika : konstrukcje, technologie, zastosowania

2005

Vol. 46, nr 2-3

50-51

Modelowano tranzystor HFET oparty na heterostrukturze AlGaN/GaN/AI₂O₃ z uwzględnieniem wpływu polaryzacji spontanicznej i piezoelektrycznej w naprężonej warstwie AlGaN. Polaryzacja warstwy AIGaN pozwala na konstruowanie niedomieszkowanych HFET. Badano wpływ polarności warstw na działanie przyrządu. Jedynie wartswy o polarności galowej okazały się przydatne do konstrukcji HFET. Uwzględniono specjalne metody obniżania koncentracji elektronów.

HFET based on AlGaN/GaN/AI₂O₃ heterostructure have been modelled. Influence of spontaneous and piezoelectric polarisation effect in strained AlGaN layer was included in modelled structures. Polarisation of AlGaN layer allows building undoped HFET. Influence of AIII-N layers polarity on device performance was modelled. Only Ga-face structures appeared suitable for HFET construction. Models took into account special methods of lowering intrinsic electron concentration as it is crucial for proper device performance.

Computer modelling of devices based on AlGaN/GaN heterostructure

Kośnikowski W., Piasecki T.

Optica Applicata

2002

Vol. 32, nr 3

485-491

Computer simulation of AlGaN/GaN heterostructure heterostructure field effect transitior (HFET) and metal–semiconductor–metal (MSM) photodetector has been performed. The influence of AlGaN layer thickness and background electron concentration, as well as piezoelectric effect, on devices’ parameters has been investigated. The results confirm the great importance of keeping low background electron concentration. The superiority of devices with AlGaN layer applied is shown. Thickness of AlGaN layer is not an important factor.

Computer controlling of MOVPE process

Piasecki T., Kośnikowski W., Paszkiewicz B., Panek M.

Optica Applicata

2002

Vol. 32, nr 3

417-420

The metalorganic vapour phase epitaxy (MOVPE) technology requires precise control of growth process. Systems designed and built in our laboratory are equipped with two microcontroller-based device. The first one is used for driving pneumatic valves, mass flow controllers and pressure controllers, the second one is responsible for PID control of epitaxial reactor temperature. This paper describes the software designed to supervise both of these devices in order to make using of MOVPE system more efficient and less error-prone, as well as to provide help in emergency situations