Diamond power devices: state of the art, modelling, figures of merit and future perspective

Abstract

With its remarkable electro-thermal properties such as the highest known thermal conductivity (~22 W cm−1∙K−1 at RT of any material, high hole mobility (>2000 cm2 V−1 s−1), high critical electric field (>10 MV cm−1), and large band gap (5.47 eV), diamond has overwhelming advantages over silicon and other wide bandgap semiconductors (WBGs) for ultra-high-voltage and high-temperature (HT) applications (>3 kV and >450 K, respectively). However, despite their tremendous potential, fabricated devices based on this material have not yet delivered the expected high performance. The main reason behind this is the absence of shallow donor and acceptor species. The second reason is the lack of consistent physical models and design approaches specific to diamond-based devices that could significantly accelerate their development. The third reason is that the best performances of diamond devices are expected only when the highest electric field in reverse bias can be achieved, something that has not been widely obtained yet. In this context, HT operation and unique device structures based on the two-dimensional hole gas (2DHG) formation represent two alternatives that could alleviate the issue of the incomplete ionization of dopant species. Nevertheless, ultra-HT operations and device parallelization could result in severe thermal management issues and affect the overall stability and long-term reliability. In addition, problems connected to the reproducibility and long-term stability of 2DHG-based devices still need to be resolved. This review paper aims at addressing these issues by providing the power device research community with a detailed set of physical models, device designs and challenges associated with all the aspects of the diamond power device value chain, from the definition of figures of merit, the material growth and processing conditions, to packaging solutions and targeted applications. Finally, the paper will conclude with suggestions on how to design power converters with diamond devices and will provide the roadmap of diamond device development for power electronics.

Progress in semiconductor diamond photodetectors and MEMS sensors

“…By virtue of the extreme hardness, diamonds are widely used as abrasive materials in industry, such as grinding tools, blades and for cutting, drilling, and polishing, etc [1][2][3][4][5]. In addition to the outstanding mechanical properties, diamond also has the highest figure-of-merits for semiconducting devices due to its extraordinary properties such as the ultra-wide bandgap (UWBG) energy, the highest thermal conductivity (22 W/mm K), high carriers mobilities, large breakdown electric field (exceeding 10 MV/cm), high chemical inertness, and thermal stability [6][7][8][9].…”

Microwave diamond devices technology: Field‐effect transistors and modeling

“…8 As shown in Table 2, the types of diamond crystals are usually classified by impurity concentration (nitrogen or boron). 9…”

“…To solve this problem, Yamada et al synthesized a mosaic diamond wafer with a size of 40 × 60 mm 2 , which consisted of 24 10 × 10 mm 2 single‐crystal diamond plates 8 . As shown in Table 2, the types of diamond crystals are usually classified by impurity concentration (nitrogen or boron) 9 …”

High temperature operation of a monolithic bidirectional diamond switch

“…Diamond meets these requirements thanks to its attractive physical properties, particularly its high breakdown field (up to more than 10 MV/cm) and superior thermal conductivity (22 W/cm.K). A focus is made on high temperature and high blocking voltage applications in which it is considered that diamond has the greatest potential [1]. In recent years diamond based power MOSFETs have been demonstrated [2]- [7], mostly relying on the surface transfer doping effect [8] (HFET) due to their relative ease of fabrication compared to the more standard MOSFET architectures (which require both p-type and n-type doping in the same device).…”