Influence of Different Surface Morphologies on the Performance of High-Voltage, Low-Resistance Diamond Schottky Diodes

Abstract

Vertical diamond Schottky diodes with blocking voltages VBD > 2.4 kV and on-resistances R On < 400 mΩcm 2 were fabricated on homoepitaxially grown diamond layers with different surface morphologies. The morphology (smooth asgrown, hillock-rich, polished) influences the Schottky barrier, the carrier transport properties, and consequently the device performance. The smooth as-grown sample exhibited a low reverse current density JRev < 10 -4 A/cm 2 for reverse voltages up to 2.2 kV. The hillock-rich sample blocked similar voltages with a slight increase in the reverse current density (JRev < 10 -3 A/cm 2 ). The calculated 1D-breakdown field, however, was reduced by 30 %, indicating a field enhancement induced by the inhomogeneous surface. The polished sample demonstrated a similar breakdown voltage and reverse current density as the smooth as-grown sample, suggesting that a polished surface can be suitable for device fabrication. However, a statistical analysis of several diodes of each sample showed the importance of the substrate quality: A high density of defects both reduces the feasible device area and increases the reverse current density. In forward direction, the hillock-rich sample exhibited a secondary Schottky barrier, which could be fitted with a modified thermionic emission model employing the Lambert W-function. Both polished and smooth sample showed nearly ideal thermionic emission with ideality factors 1.08 and 1.03, respectively. Compared with literature, all three diodes exhibit an improved Baliga Figure of Merit for diamond Schottky diodes with VBD > 2 kV.

Enhanced in-plane uniformity and breakdown strength of diamond Schottky barrier diodes fabricated on heteroepitaxial substrates

“…Since we used an as-grown diamond surface for fabricating SBDs, mechanical polishing is an effective way to reduce the n value to close to unity. 26) Table I summarizes the distribution of n and f B values for diamond SBDs grown on different kinds of substrates. The SDs of each diode parameter were evidently decreased after insertion of the MAT buffer layer, indicating that the homogeneity of the metal-semiconductor interface was improved.…”

Analytic modeling of a hybrid power module based on diamond and SiC devices

“…Thanks to its outstanding thermal and electrical properties, diamond is expected to improve significantly the performance of the next generation of power semiconductor devices, as presented in [1,2,3]. Numerous devices have been already presented in the literature, from diamond Schottky diodes to vertical Field Effect Transistors [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. Diamond thermal substrate can also be used solely for its highest thermal conductivity such as in [19].…”

Impact of Laser‐Induced Graphitization on Diamond Schottky Barrier Diodes

“…Diamond-based electronics are promisingly expected as nextgeneration power and high-speed switching devices with low switching loss, even operable under extreme conditions. [1][2][3][4] This is due to its superior properties such as an ultrawide bandgap of 5.5 eV, high mobilities of 4500 cm 2 V À1 s À1 for electron and 3800 cm 2 V À1 s À1 for hole, [5,6] high breakdown strength (E max ) of 10 MV cm À1 , [7] and the highest Baliga's and Huang's figures of merit compared with other wide-bandgap semiconductors. [8,9] In addition, because diamond possesses the largest thermal conductivity of 22 W cm À1 K À1 among bulk materials, [10] the large displacement energy as well as the high chemical inertness and thermal durability, [11,12] the radiation, and the high-temperature proof operation can be expected.…”