## 3 Results
At 150 K, the planar devices had more than one order of magnitude higher dark current, which must be addressed, especially for high operation temperature (HOT) aspects. This degradation of dark current at high temperatures for the planar SLS devices can be related to the nature of the defects created by the ion-implantation process and annealing treatment [23]. Further empirical and simulation studies of different aspects of ion-implantation for SLS material are strongly recommended. However, the outcome of this research would be a useful guideline for future work. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Design**} & **Implantation** & **Implantation** & **Depth of Ion** & \multirow{2}{*}{**Straggling**} \\  & **Energy** & **Dose** & **Concentration Peak** & \\ \hline \(pBn\) & 300 KeV & \(1\times 10^{15}\) cm\({}^{-2}\) & 900 nm & 100 nm \\ \(nBn\) & 380 KeV & \(1\times 10^{15}\) cm\({}^{-2}\) & 1000 nm & 115 nm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Optimized implantation parameters for the \(pBn\) and \(nBn\) designs. Figure 4: (**a**) Dark current density vs. applied bias voltage of the optimized ion-implantation condition at 77K and 150 K for MWIR \(nBn\) (**a**) and \(pBn\) (**b**) planar devices. The inset of each part compares the dark current density values for planar and mesa-etched photodetectors at 77, 100, and 150 K. All diodes were circular with a 200-\(\upmu\)m diameter. The comparison of the optical performance of both MWIR planar devices under optimized implantation at 77 K and 150 K is shown in Figure 5a,b. The calculated saturated QE values of both devices were also compared with the mesa-isolated devices. For the optical test, the top illumination approach was chosen with no anti-refection coatings, and a calibrated 1000 \({}^{\circ}\)C blackbody source and Fourier transform infrared (FTIR) spectrometer were used. For the \(nBn\) and \(pBn\) planar devices, saturated QE values were calculated at \(-80\) mV and \(-40\) mV bias voltage, respectively. The 50% cut-off wavelength for the \(nBn\) planar device at 77 K, was 4.10 \(\upmu\)m, with a saturated peak responsivity (R\({}_{\text{i}}\)) of 0.67 A/W at \(\uplambda=3.35\)\(\upmu\)m at a \(-80\) mV applied bias. At 150 K, the saturated peak responsivity was 0.84 A/W at the same wavelength, with a 50% cut-off wavelength 4.40 \(\upmu\)m. For the \(pBn\) device at 77 K and a \(-40\) mV bias voltage, the 50% cut-off wavelength of the planar device was 4.40 \(\upmu\)m with a peak responsivity of 0.76 A/W at 3.8 \(\upmu\)m. At 150 K, the peak responsivity increased to 1.09 A/W. The corresponding saturated QE values at peak responsivity for both planar devices are summarized in Table 2, along with relevant QE values for mesa-isolated devices. The specific detectivity (\(D^{\bullet}\)) values for both SLS structures have also been calculated for the optimized implantation parameters and compared with the mesa-etched device (Figure 6a,b). The \(D^{\bullet}\) values were calculated by the equation shown in Figure 6b at given applied bias for the peak responsivity provided earlier. Overall, for planar devices and similar to reticulated structures, a steady trend for the specific detectivity values were observed for the MWIR spectrum across a broad range of wavelengths, which is promising for different applications that require broad-band photodetection. This can offer a possible \begin{table}
\begin{tabular}{c c c c} \hline
**Design** & **Fabrication Approach** & **QE @ 150 K** & **QE @ 77 K** \\ \hline \(nBn\) & Mesa & 36.4\% & 25.0\% \\ \(\uplambda=3.35\)\(\upmu\)m & Planar & 31.5\% & 23.5\% \\ \(pBn\) & Mesa & 39.2\% & 24.4\% \\ \(\uplambda=3.80\)\(\upmu\)m & Planar & 32.6\% & 21.5\% \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison of the QE values at peak responsivity for planar and mesa-isolated SLS devices at 77 and 150 K. (V\({}_{\text{b}}=-40\) mV for \(pBn\) and V\({}_{\text{b}}=-80\) mV for \(nBn\)).