| Abstract Scope |
There has been great interest in GaN and related alloys due to their superior properties compared to many semiconductors, such as high breakdown field, good thermal conductivity and high electron saturation velocity. While Al<SUB>x</SUB>Ga<SUB>1-x</SUB>N is important for power devices and deep ultraviolet emitters, In<SUB>x</SUB>Ga<SUB>1-x</SUB>N alloys with band-gaps ranging from 0.7-3.4 eV covering the entire visible spectrum are of interest for many future optoelectronic and energy applications. In addition, high In composition In<SUB>x</SUB>Ga<SUB>1-x</SUB>N alloys also possess significant potential for high speed device applications due to small effective mass and high mobility. For all such device applications, device characteristics and performance are greatly impacted, and degraded, by the presence of variety of growth related defects. This study focuses on the presence and electronic properties of deep levels in InGaN materials growth by nitrogen plasma-assisted molecular beam epitaxy (PAMBE). PAMBE was used to grow 300 nm thick, undoped In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N layer on an n-type GaN template. The In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N composition was confirmed by high resolution triple-axis X-ray diffraction measurements. Schottky diode (SD) properties of semitransparent Pt(8nm) and Au(4nm)/Ag(4nm) metals on In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N were investigated and defect characterization was performed using capacitance deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS), which together make possible deep levels detection throughout In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N band-gap. From I-V characterization of the SDs, it is shown that Au/Ag/In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N SDs have lower reverse current density, higher barrier height (φ<SUB>b</SUB>=0.67eV), and lower ideality factor (n=2), compared to Pt diode produced in this study and Pt SDs in the literature[1]. C-V measurements show that the In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N layer has an n-type background doping concentration of 6x10<SUP>17</SUP>cm<SUP>-3</SUP>. DLTS measurements displays two electron traps (E<SUB>t1</SUB> and E<SUB>t2</SUB>) peaking at 227 K and 384 K for 10 s<SUP>-1</SUP> rate window, respectively. Defect energies and capture cross section values of the E<SUB>t1</SUB> and E<SUB>t2</SUB> levels were determined to be Ec-0.39eV, 1.24x10<SUP>-16</SUP>cm<SUP>2</SUP> and Ec-0.91eV, 6.28x10<SUP>-14</SUP>cm<SUP>2</SUP>, respectively, with nearly identical concentrations of 1.2x10<SUP>15</SUP> cm<SUP>-3</SUP>. In order to probe the defect states located in the lower half of the band-gap, DLOS measurements were performed using a monochromatized Xe lamp with photon energies between 1.2-3.6 eV. Analysis of the DLOS optical cross sections revealed three additional defect levels, with energies of at 1.4, 1.76 and 2.5 eV below the conduction band. The concentrations of those deep levels are 1.33x10<SUP>15</SUP>, 3.15x10<SUP>15</SUP> and 6.13x10<SUP>16</SUP>cm<SUP>-3</SUP>, respectively. In this work, we have demonstrated Au/Ag/In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N SDs and used it for studying the deep levels throughout In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N band-gap. Five deep levels were observed throughout the band-gap of the In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>N. Full details of these 5 traps in InGaN, their possible role in carrier compensation, and their relation to possible physical sources, will be further described. |