Transfer of AlGaN/GaN RF-devices onto diamond substrates via van der Waals bonding

We present a new bonding process for gallium nitride (AlGaN/GaN) devices from Si onto diamond substrates. In our technology AlGaN/GaN-devices are transferred from silicon (Si) onto single (SCD) and polycrystalline diamond (PCD) substrates by van der Waals bonding. Load-pull measurements on Si and SCD at 3 GHz and 50 V drain bias show comparable power-added-efficiency (PAE) and output power (Pout) levels. Also, comparisons of 2x1 mm GaN-diodes on Si, PCD, and SCD reveal significantly increased power levels. In summary, we show a promising new GaN-on-diamond technology for future high power, microwave GaN-device applications

Transfer of AlGaN/GaN RF-devices onto diamond substrates via van der Waals bonding

We present a new bonding process for galliumnitride (AlGaN/GaN) devices from Si onto diamond substrates. In our technology AlGaN/GaN-devices are transferred from silicon (Si) onto single (SCD) and polycrystalline diamond (PCD) substrates by van der Waals bonding. Load-pull measurements on Si and SCD at 3 GHz and 50 V drain bias show comparable power-added-efficiency (PAE) and output power (Pout) levels. Also, comparisons of 2x1 mm GaN-diodes on Si, PCD, and SCD reveal significantly increased power levels. In summary, we show a promising new GaN-on-diamond technology for future high power, microwave GaN-device applications

3 GHz RF measurements of AlGaN/GaN transistors transferred from silicon substrates onto single crystalline diamond

The integration of AlGaN/GaN thin film transistors onto diamond substrates enables the efficient dissipation of device heat, thus providing a boost in performance and reliability of current high-frequency GaN power amplifiers.In this paper,we show 3GHz load-pull measurements of GaN transistors on silicon(Si) and single crystalline diamond(SCD) as fabricated by our recently presented direct low-temperature bond process. After the transfer onto SCD, the efficiency and output power are increased by 15%, which is explained by a calculated temperature difference of∼100 K. In addition, the temperature between individual gate fingers is reduced such that the output power density (Pout) is independent of the amount of fingers. A drawback of our GaN epilayer is identified in the huge thermal resistance of the buffer layer so that the heat spreading performance of our technology is significantly impaired. Nevertheless, we demonstrate a largeGaN-on-diamond output power of 14.4 WataPout of 8.0W/mm

Pseudovertical Schottky Diodes on Heteroepitaxially Grown Diamond

Substrates comprising heteroepitaxially grown single-crystalline diamond epilayers were used to fabricate pseudovertical Schottky diodes. These consisted of Ti/Pt/Au contacts on p− Boron-doped diamond (BDD) layers (1015–1016 cm−3) with varying thicknesses countered by ohmic contacts on underlying p+ layers (1019–1020 cm−3) on the quasi-intrinsic diamond starting substrate. Whereas the forward current exhibited a low-voltage shunt conductance and, for higher voltages, thermionic emission behavior with systematic dependence on the p− film thickness, the reverse leakage current appeared to be space-charge-limited depending on the existence of local channels and thus local defects, and depending less on the thickness. For the Schottky barriers ϕSB, a systematic correlation to the ideality factors n was observed, with an “ideal” n = 1 Schottky barrier of ϕSB = 1.43 eV. For the best diodes, the breakdown field reached 1.5 MV/cm

Pseudovertical Schottky Diodes on Heteroepitaxially Grown Diamond

Substrates comprising heteroepitaxially grown single-crystalline diamond epilayers were used to fabricate pseudovertical Schottky diodes. These consisted of Ti/Pt/Au contacts on p− Boron-doped diamond (BDD) layers (1015–1016 cm−3) with varying thicknesses countered by ohmic contacts on underlying p+ layers (1019–1020 cm−3) on the quasi-intrinsic diamond starting substrate. Whereas the forward current exhibited a low-voltage shunt conductance and, for higher voltages, thermionic emission behavior with systematic dependence on the p− film thickness, the reverse leakage current appeared to be space-charge-limited depending on the existence of local channels and thus local defects, and depending less on the thickness. For the Schottky barriers ϕSB, a systematic correlation to the ideality factors n was observed, with an “ideal” n = 1 Schottky barrier of ϕSB = 1.43 eV. For the best diodes, the breakdown field reached 1.5 MV/cm

Monolithic GaN power circuits for highly-efficient, fast-switching converter applications with higher functionality

The AlGaN/GaN-on-Si high-voltage technology has received significant attention over the past several years. Fast improvements in terms of static and especially dynamic properties of AlGaN/GaN HEMTs have been achieved. Compared to conventional (vertical) technologies such as IGBTs or power MOSFETs, the lateral GaN-on-Si technology features the possibility to integrate multiple high-voltage devices on a single chip. Monolithic integration is desirable for several reasons, including reduced costs in terms of assembly and reduced chip area. Furthermore, a more compact switching cell leads to the reduction of parasitic inductances and capacitances, which opens opportunities for high efficiency operation and higher switching frequencies as well as improved reliability. It is anticipated that monolithic integration in lateral wide bandgap technology will lead to substantially improved size, efficiency and cost trade-offs in power conversion applications. Additionally, a higher functionality of the chip is desired in order to extend the range of applications. A monitoring of the precise in-chip temperature enables an optimum control of the operation adapted to the matters of the application