Electrically Active Deep Levels in ScN
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Electrically Active Deep Levels in ScN Florentina Perjeru, Xuewen Bai and Martin E. Kordesch Department of Physics and Astronomy, Ohio University, Athens Oh 45701 ABSTRACT We report the electronic characterization of n-ScN in ScN-Si heterojunctions using Deep Level Transient Spectroscopy of electrically active deep levels. ScN material was grown by plasma assisted physical vapor deposition and by reactive sputtering on commercial p+ Si substrates. Deep level transient spectroscopy of the junction grown by plasma assisted physical vapor deposition shows the presence of an electronic trap with activation energy EC-ET= 0.51 eV. The trap has a higher concentration (1.2-1.6×1013cm-3) closer to the ScN/Si interface. Junctions grown by sputtering also have an electronic trap, situated at about EC-ET= 0.90 eV.
INTRODUCTION Transition-metal nitrides are well known for their remarkable physical properties. As a result, they are widely studied and have become technologically important for applications such as hard wear-resistant coatings, diffusion barriers, and optical coatings. While TiN has received by far the most attention and is presently used commercially in all of the above applications, the neighboring nitride on the periodic table, ScN, is less often used [1]. ScN is a group 3-15 material but little is known about its electrical and optical properties. Theoretical calculations indicate that ScN has an indirect band gap of 0.90 eV and a direct one of 2.20 eV [2] but experimentally the direct gap at 2.2 eV dominates, the presence of the indirect gap has yet to be confirmed [3]. ScN crystallizes in cubic form (rock-salt structure) [3] with lattice constant a = 4.48Å. ScN material has been grown by a variety of techniques [4,5]. From the electronic point of view, there is little reported so far on the formation and behavior of metallic contacts on ScN [6]. In addition, there are few reports on junction formation using ScN, homo- or hetero- junctions with other materials [7,8]. In this study the presence of deep levels in ScN material was investigated using Deep Level Transient Spectroscopy (DLTS). With DLTS, deep levels are commonly investigated in the space-charge region of rectifying devices, such as Schottky barriers or p-n junctions. The p-n junctions are used when a Schottky barrier can not be obtained. ScN-Si p-n heterojunctions were used for this study. The ohmic contacts were fabricated using dc-sputtered Pd for ScN and evaporated Al for Si (thickness 1000 Å). Details on contact formation can be found in Ref [7]. Current-voltage measurements were conducted at 300 K using a Keithley 236 source measure unit. Capacitance-voltage and DLTS measurements were performed in vacuum at a pressure of 1x 10-3 Torr and at a frequency of 1 MHz using a SULA Technologies R3.6.1
Deep Level Transient Spectrometer . The samples were heated indirectly using a power resistor while the cooling was done using liquid nitrogen. The sample temperature, needed for Arrhenius analysis, was measured with a thermocouple and a Eurotherm tempe
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