# Design and Analysis of Heavily Doped n+
## 2 The Proposed Device Structure
### Proposed Heavily Doped n\({}^{+}\) Pocket AJ DG MOSFET with a Nanogap-Cavity Region  
Figure 4a shows n\({}^{+}\) pocket AJ DG MOSFET with a cavity region. A cavity is introduced in the gate oxide region and is filled with the dielectric material. The length (L\({}_{\text{cavity}}\)) and height (H\({}_{\text{cavity}}\)) of the nanogap cavity region was varied along with different dielectric materials to analyze the device sensitivity to detect biomolecules. The different dielectric materials selected were air, SiO\({}_{2}\), HfO\({}_{2}\) and S\({}_{3}\)N\({}_{4}\). The detection phenomena are based on the electrical parameters like the dielectric constant. The height (H\({}_{\text{cavity}}\)) of the nanogap cavity taken is 1 nm in Figure 4a. The n\({}^{+}\) pocket AJ DG MOSFET with nanogap cavity and thin SiO\({}_{2}\) a layer is shown in Figure 4b for binding the molecules entering  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Device Structure** & \begin{tabular}{c} \(I_{ON}\) \\ **(A/\(\mu\)m)** \\ \end{tabular} & \begin{tabular}{c} \(I_{OFF}\) \\ **(A/\(\mu\)m)** \\ \end{tabular} & \begin{tabular}{c} \(I_{ON}\)/\(I_{OFF}\)** \\ **(mV/dec)** \\ \end{tabular} & \
\begin{tabular}{c} **SS=\(\frac{dV_{m}}{d(logI_{d})}\)** \\ **(mV/V)** \\ \end{tabular} &
\begin{tabular}{c} **DIBL=\(\frac{dV_{m}}{dV_{m}}\)** \\ **Length** \\ **(nm)** \\ \end{tabular} \\ \hline AJ DG MOSFET, (2016) & \(127\times 10^{-6}\) & 0.001\(\times 10^{-9}\) & \(1.27\times 10^{5}\) & 68 & 65 & 20 \\ DG MOSFET & – & – & \(4.03\times 10^{9}\) & 63.34 & 79.58 & 20 \\ n\({}^{+}\) Pocket AJ DG MOSFET & \(1.88\times 10^{-4}\) & \(9.7\times 10^{-17}\) & \(-10^{13}\) & 59 & 13.4 & 20 \\ (proposed work) & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Performance comparison of proposed n\({}^{+}\) pocket AJ DG MOSFET with available DG MOSFET device structures.  
Figure 3: Drain current variations concerning gate voltage for heavily doped n\({}^{+}\) pocket AJ DG MOSFET.  
the cavity region, restricting their movements. The height of the cavity region (H\({}_{\text{cavity}}\)) was 2.7 nm and the thin layer of SiO\({}_{2}\) was 0.3 nm. The device sensitivity for the detection of biomolecules was analyzed by introducing different types of charged particles into the cavity region. The nanogap cavity region can be formed by a thin layer deposition technique followed by a wet etching process. The AJ DG MOSFET with the cavity region works using the dielectric modulation technique for the detection of biomolecules based on the shifting of threshold voltage by variation in dielectric properties. Dielectrically modulated (DM) AJ DG MOSFET is highly sensitive to change in the dielectric constant in the cavity region. However, there are many biomolecules like DNA, enzymes, etc., which contain a charge. The working of the DM AJ DG MOSFET is affected by the presence of charge biomolecules when it enters the nano-gap cavity along with the presence of the constant dielectric effect. Therefore, Figure 4b shows the charge effect of biomolecules along with the effect of the dielectric constant.