Dehzangi et al. Nanoscale Research Letters 2012, 7:381 http://www.nanoscalereslett.com/content/7/1/381 reported JLTs in which there were more interfaces with the gate oxide layer or BOX and more current values after increasing the negative gate voltage for p-type channels. Here, we only have one interface between the channel and the BOX in order to provide charge accumulation. Ac- cordingly, the increasing negative gate voltage is not able to produce more current compare to the trigate FETs, Fin FETs, GAA FETs, or reported JLTs. For our SG and DGJLTs as gated resistors, when the device is turned on, these essentially behave as a resistor, and the drain current is controlled by regions I and II and doping concentration. For linear region ID could be given approximately by [47]: ID≈qμNA TW L VDS: 1 ð Þ 2 ð Þ Where is the semiconductor doping concentration, μ is the effective mobility, q is the electron charge; T, W, and L are the thickness, width, and the length of the chan- nel respectively. Equation 1 was first time suggested by Colinge [9] for JLTs and also by Fonash et al. [52] who also suggested the similar equation before Colinge’s group about the accumulation mode of unipolar Si nanowire transistors. This equation points out that ID is controlled by the doping concentration NA, and not by the gate cap- acitance per area C. We believe that the ID equation in our case would be very similar to Equation 1. For high doping concentration cases, which were mostly considered in literatures for JLTs, Equation 1 is suggesting for linear region. In our case, considering the on state device, low concentration profile for the p-type material, and also the effect of the fins at the side of the channel to the source and the drain contacts, we suggest the same equation, un- less, for the VDS we have effective voltage for the channel VCh, which is obeying the jVChj < jVDSj. Then, we have ID≈qμNA TW L VCh: In the on state condition, for a given VDS, the electric field from the source to the negatively biased drain must be significantly small (nearly zero) in the neutral wire at the center of the channel. In the linear region we expect that the negative charge in region I (Figure 7), which is adjacent to the area of I/II interface, should be gathered. This charge in the p-type material can only come from depletion in the channel in linear region. In our case to enter the saturation region from linear region and since the device is trying to reach the satur- ation condition, we propose that we would have the con- dition at which the effective channel voltage become fixed at VSCaht. Then, further increases in VDS, take place across the channel region and causes the negative charge (electrons) accumulation at the two sides of the channel near the source and the drain interfaces with channel Page 7 of 9 and also in VCShat < jVDSj: Considering the Colinge et.al suggestion [47] for saturation region, we have TW IDSat≈qμNA 2L VCShat 2: 3 ð Þ This equation can be compared with the general expres- sion of drain current for conventional MOSFETs in the saturation region or even in the accumulation mode [53]. In addition, because of the presence of ohmic con- tacts for the majority carriers and their location, which is away from the channel edges, we will not have any ambipolar behavior. Unfortunately, the transistors showed leakage through the gate electrode when gate voltages exceeded −3 V. However, the device worked was acceptable for gate voltages smaller than −3 V and gave us some information to confirm our simple model. Conclusions The DG and SGJLT were fabricated by AFM-LAO nano- lithography on low doped p-type SOI, followed by two improved wet etching process. We do not have a con- ventional situation for above the threshold voltage and channel saturation, since the devices are gated resistor and on state pinch off transistor. Then negative VG can- not provide the accumulation in channel, but the pinch off occurs alike in a regular junctionless field-effect tran- sistor. The output and transfer characteristic comparison of DG and SG structures were shown and the simple model according to the JLT principal. Competing interest The authors declare that they have no competing interests. Authors’ contributions AD designed and carried out the experimental work, conducted basic characterizations of the sample, analyzed all the data, the model description, and wrote the manuscript. AMA performed the TEM observations and participated in characterization. FL conceived of the study and participated in the experimental work, design, and coordination. SDH participated in the sequence alignment and provided the AFM and SPA instruments. EBS and MNH supervised the research work. JH critically revised the manuscript and YG participated in sequence alignment. All authors read and approved the final manuscript. Acknowledgements The authors gratefully acknowledge that this work was financially supported by the Science Fund from the Ministry of Science, Technology and Innovation (MOSTI), Malaysia, under project no. 03-01-05-SF0384, the USM Short Term Grant under project number 304/PBAHAN/6039035, and UPM FRGS number 5524051. Author details 1Department of Physics, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia. 2School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Nibong Tebal, Penang 14300, Malaysia. 3Functional Devices Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia. 4Department of Chemistry, Islamic Azad University, Behbahan Branch University Street, Behbahan 6361713198, Iran. Received: 23 March 2012 Accepted: 29 June 2012 Published: 11 July 2012