Toward flexible, multi-device, and on-demand P-N junction manipulation in reconfigurable circuits

When applied to ultrathin-body P-N diodes, electrostatic doping can elicit a gate-induced electron (negative) or hole (positive) charge. In applied physics, it has been theorized that a virtual P-N junction could be achieved by applying a positive voltage to a diode’s back gate and a negative voltage to the diode’s underlapped front gate. However, a dearth of experimental data exists that would show if the virtual P-N junction with electrostatic doping behaves similarly to that of a physical P-N diode. Researchers at the Grenoble Institute of Technology in France investigate this theory in Journal of Applied Physics.

The authors employ an ultrathin, nano-sized PIN diode with state-of-the art Fully Depleted Silicon On Insulator (FD-SOI) technology, a gate underlap, a thin buried oxide (BOX), and equal lengths of gated P and ungated N regions, all of which give the diode the versatility to measure the reverse and forward currents for various front gate and ground-plane biases. The researchers also used Synopsys Sentaurus, a multidimensional device simulator software tool, to numerically simulate diode mechanisms.

The paper notes that virtual P and N doping results in a standard diode-like current-voltage (I-V) curve. However, after a deeper examination of distinct regions within the reverse and forward currents, the authors concluded that despite this “diode-like” behavior, the virtual and physical diodes, in fact, behave differently since the intrinsic gate-induced charge concentration varies dynamically with bias.

Coauthor Sorin Cristoloveanu says the observed behavior demonstrates the virtual diode’s flexible interchanging of N and P regions in nine different devices including virtual and semi-virtual diodes. Cristoloveanu adds, “This offers opportunities for on-demand P-N junction manipulation in reconfigurable circuits and simpler ultrathin semiconductor layer characterization.”

Source: “A reconfigurable silicon-on-insulator diode with tunable electrostatic doping,” by Sorin Cristoloveanu, Kyung Hwa Lee, and Maryline Bawedin, Journal of Applied Physics (2017). The article can be accessed at https://doi.org/10.1063/1.4999314 .