Tracking the Effect of Adatom Electronegativity on Systematically Modified AlGaN/GaN Schottky Interfaces

Abstract

The influence of surface modifications on the Schottky barrier height for gallium nitride semiconductor devices is frequently underestimated or neglected in investigations thereof. We show that a strong dependency of Schottky barrier heights for nickel/aluminum-gallium nitride (0001) contacts on the surface terminations exists: a linear correlation of increasing barrier height with increasing electronegativity of superficial adatoms is observed. The negatively charged adatoms compete with the present nitrogen over the available gallium (or aluminum) orbital to form an electrically improved surface termination. The resulting modification of the surface dipoles and hence polarization of the surface termination causes observed band bending. Our findings suggest that the greatest Schottky barrier heights are achieved by increasing the concentration of the most polarized fluorine-gallium (-aluminum) bonds at the surface. An increase in barrier height from 0.7 to 1.1 eV after a 15% fluorine termination is obtained with ideality factors of 1.10 ± 0.05. The presence of surface dipoles that are changing the surface energy is proven by the sessile drop method as the electronegativity difference and polarization influences the contact angle. The extracted decrease in the Lifshitz-van-der-Waals component from 48.8 to 40.4 mJ/m(2) with increasing electronegativity and concentration of surface adatoms confirms the presence of increasing surface dipoles: as the polarizability of equally charged anions decreases with increasing electronegativity, the diiodomethane contact angles increase significantly from 14° up to 39° after the 15% fluorine termination. Therefore, a linear correlation between increasing anion electronegativity of the (Al)GaN termination and total surface energy within a 95% confidence interval is obtained. Furthermore, our results reveal a generally strong Lewis basicity of (Al)GaN surfaces explaining the high chemical inertness of the surfaces.

Electron Doping BaZrO3 via Topochemical Reduction

“…BZO’s high degree of chemical stability makes it an attractive candidate for utilization in harsh environments. Some of its appealing features are wide band gap (5.3 eV), ease of doping, , and low electron affinity. ,, Electron affinity and work function play a critical role in electrochemical reactions such as oxygen reduction and CO oxidation, the electrical properties of heterojunctions in complex oxides and nitrides, and the efficiency of electron emission and photoemission devices . Frequently, the low electron affinity or work function of the materials is beneficial to drive these processes.…”

“…4,7,8 Electron affinity and work function play a critical role in electrochemical reactions such as oxygen reduction 9 and CO oxidation, 10 the electrical properties of heterojunctions in complex oxides 11 and nitrides, 12 and the efficiency of electron emission and photoemission devices. 12 Frequently, the low electron affinity or work function of the materials is beneficial to drive these processes. Hence, low electron affinity materials, which are stable under adverse conditions, can find a wide variety of applications.…”

Thermal effect of Zn quantum dots grown on Si(111): competition between relaxation and reconstraint

“…The lattice and pattern matching between the metal and semiconductor surfaces are correlated with interface structure and electrical properties and determine the state of a metallic contact coherently grown on the semiconductor [5][6][7]. Defect-free contacts can reduce leakage currents, stabilize heating treatment, and produce accurate surface states, which stabilize the Schottky barrier height of the interface [8][9][10]. The interface between the metal contact and multilayer semiconductor systems, such as laser diodes, field-effect transistors, and gas sensors, cannot be metallized because annealing would damage the fine structures in the interfaces of multilayer semiconductor systems [11][12][13].…”