(Al,SC) N SLUOKSNIŲ TYRIMAS DINAMINIŲ DIFRAKCINIŲ GARDELIŲ METODU

Ištrauka

(Al,SC) N SLUOKSNIŲ TYRIMAS DINAMINIŲ DIFRAKCINIŲ GARDELIŲ METODU
BAKALAURO STUDIJŲ BAIGIAMASIS DARBAS

TABLE OF CONTENTS
1.INTRODUCTION 4
2.LITERATURE ANALYSIS 5
2.1.AlN, ScN, Al1-xScxN 5
2.2.Growth conditions influence on Al1-xScxN quality 7
3.METHODOLOGY 9
3.1.Samples: wurtzite Al1-xScxN 9
3.2.Light induced transient grating measurements 9
3.3.Data processing 13
4.RESULTS 15
4.1.LITG measurements 15
5.CONCLUSIONS 19
6.SANTRAUKA 20
7.REFERENCES 21

1. INTRODUCTION
Aluminum nitride (AlN) has become a typical material for producing micro electro-
mechanical systems (MEMS) devices, energy harvesting systems, ultrasonic transducers,
chemical sensors, accelerometers, film bulk acoustic resonators (FBAR) duplex filters
because of its unique properties such as high acoustic velocity, wide band gap, high Curie
temperature, high- temperature stability, high hardness, high thermal conductivity, high
electrical resistivity, and low acoustic loss 1,2. Among tetrahedrally bonded binary
semiconductors, AlN has the highest piezoelectric coefficient, making it a preferred choice for
fabrication of many devices 3. However, its implementation in wide band communication 3,
sensors, and filters 1 is limited by its relatively low electromechanical coupling factor (keff),
which is around 6%-7%4, comparably lower than in other commercially used materials such
as α-quartz with keff < 8.8% or GaPO4 with keff = 13%.
AlN alloy with Sc gathers much interest from the scientists as it offers 5 times higher
piezoelectricity than AlN films 5 as well as a lower stiffness constant 3,6. Furthermore, a
possibility to tune the bandgap in the UV to visible range by changing the Sc content in the
alloy7 gathers interest as well. Al1-xScxN can be grown both as a wurtzite and rock salt
material by sputtering techniques. The cubic phase is well-suited for optoelectronic
applications, while the wurtzite phase is of interest for combining the alloy with other group
III-nitrides, enabling its use in optoelectronics spanning the green to UV spectral
range 7. Additionally, Al1-xScxN/GaN with increased piezoelectric coefficient would generate
a higher density of carriers in the 2D electron gas, making it advantageous for high electron
mobility transistors (HEMTs) 7,8.
The main aim of this work is to investigate and provide some insights on the non-equilibrium
carrier dynamics in (Al,Sc)N layers employing a light induced transient grating technique, as
it is a quite new material and such properties are yet to be reported in scientific literature.