Record performance in intrinsic, impurity-free lateral diamond photoconductive semiconductor switches

Photoconductive semiconductor switches (PCSSs) are fabricated on type IIa diamond substrates with varying boron and nitrogen impurity levels (<10¹⁴-10¹⁶ cm⁻³). The photoresponse of lateral PCSS is reported over the incident laser wavelength range (212-240 nm), energy per pulse (5-65 μJ), and DC bias (−1.2 to +1.2 kV). The PCSS device with the lowest boron and nitrogen impurity concentration achieves the highest normalized responsivity of 9.1 × 10⁻⁸ A-cm/W-V, peak photocurrent of 8.0 A, and on/off ratio of 2.3 × 10¹¹ at a DC bias of +1.2 kV with the potential for even higher currents at increased DC bias. All PCSS display fast rise times (<3 ns), limited by the laser's rise time. However, photoresponse measurements reveal that higher impurity levels reduce the photocurrent and decrease the on/off ratio. These results highlight the performance advantages of using low background concentration type IIa diamond substrates for PCSS fabrication and present a promising route toward advanced high-power, high-speed diamond-based switches.