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In this paper, we propose a method to classify the tunneling currents using simulations. The main objective is to investigate the effects of the direct source-to-drain tunneling, which is undesirable, in the case of devices with extremely short channels. We performed the classification of tunneling currents in InGaAs/GaAsSb heterojunction double-gate tunnel FETs based on this method, and we found that the direct-tunneling component increased dramatically in short-channel cases. The channel length must be 20 nm or longer, in case of InGaAs/GaAsSb heterojunction double-gate tunnel FETs, to limit the off-current within 10 pA/µm, which is required as per the ITRS LP.

Reliable detection of single electron tunneling in quantum dots (QD) is paramount to use this category of device for quantum information processing. Here, we report charge sensing in a degenerately phosphorusdoped silicon QD by means of a capacitively coupled single-electron tunneling device made of the same material. Besides accurate counting of tunneling events in the QD, we demonstrate that this architecture can be operated to reveal asymmetries in the transport characteristic of the QD. Indeed, the observation of gate voltage shifts in the detector's response as the QD bias is changed is an indication of variable tunneling rates. Silicon-based quantum dot (QD) architectures1-3 for quantum computing have recently emerged as an attractive possibility in view of their scalability, their compatibility with the widely accessible complementary metaloxide-semiconductor technology 4 and their long coherence time for electron spin states.5 In these systems, readout of qubit states typically requires charge sensing and spin-to-charge conversion.6 Nevertheless, charge sensing is useful to achieve the few-electron regime in the dot which is instrumental to perform spin manipulations.7 Demonstration of reliable single-electron detection is, therefore, crucial for the implementation of quantum logical operations and future development of complex quantum computational schemes.Here, we report charge sensing using two capacitively coupled single-electron tunneling devices (SET) fabricated in degenerately phosphorus-doped silicon. One SET is used as a QD weakly coupled to two electron reservoirs (namely, source and drain) while the remaining SET is used as a detector of the QD charge state. We show that modifications of the drain-source bias voltage of the QD can lead to changes in the transparency of its tunnel barrier(s). This results in the observation of a negative differential conductance (NDC) in the