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Electrode design parameters of MSM structures under investigation_
| Type of MSM structures | Detector area (μm2) | Finger width (μm) | Finger spacing (μm) | Fill factor (Ratio of total active optical area to total surface area) | |
|---|---|---|---|---|---|
| Equal finger width and spacing designs | 2-Fingers | 40 (39.9) | 13.33 | 13.33 (S = W) | 13.33/40 = 0.33 |
| 3-Fingers | 40 | 8 | 8 (S = W) | 16/40 = 0.40 | |
| 4-Fingers | ~40 (39.9) | 5.71 | 5.71 (S = W) | 17.13/40 = 0.43 | |
| 5-Fingers | ~40 (39.9) | 4.44 | 4.44 (S = W) | 17.76/40 = 0.44 | |
| 14-Fingers | ~40 (39.9) | 1.48 | 1.48 (S = W) | 19.24/40 = 0.48 | |
| Double finger spacing designs | 2-Fingers | 40 | 10.0 | 20.0 (S = 2W) | 20/40 = 0.50 |
| 3-Fingers | ~40 (39.9) | 5.7 | 11.4 (S = 2W) | 22.8/40 = 0.57 | |
| 4-Fingers | 40 | 4.0 | 8.0 (S = 2W) | 24/40 = 0.60 | |
| 5-Fingers | ~40 (39.9) | 3.07 | 6.14 (S = 2W) | 24.56/40 = 0.61 | |
| 6-Fingers | 40 | 2.5 | 5.0 (S = 2W) | 25/40 = 0.63 | |
| 14-Fingers | 40 | 1 | 2.0 (S = 2W) | 26/40 = 0.65 | |
Comparison of Present observations with existing MSM detectors_
| Reference of Earlier work | MSM detector Structure | Photocurrent (A) using I–V characteristics plot | Dark current density (A/cm2) |
|---|---|---|---|
| (Wang et al., 2013) | Al0.4Ga0.6N/AlN/Sapphire With S = W = 7 μm and 28 fingers | Around 3e-08 at 20 V | 1e-11 at 20 V |
| (Gökkavas et al., 2007) | Al0.6Ga0.4N/AlN/Sapphire With S = W = 4 μm and 25 fingers | - | 5.8 1e-10 at 50 V |
| Al0.5Ga0.5N/AlN/Sapphire With S = W = 3 μm and 16 fingers | - | 1.4 1e-10 at 50 V | |
| (Xie et al., 2012) | Al0.4Ga0.6N/AlN/Sapphire With S = W = 5 μm and 40 fingers | 1e-08 at 20 V | 1.25e-12 at 20 V |
| Present work | Al0.5Ga0.5N/AlN/Sapphire Based on S = W with 4 fingers | 1e-09 at 20 V | 1e-10 at 20 V |
| Al0.5Ga0.5N/AlN/Sapphire Based on S = 2W with 5 fingers | 10.725e-03 at 50 V | 9.5e-11 at 50 V |
Performance parameters of MSM structures under investigation_
| Type of MSM structure | Number of fingers | Electrode dimensions | Peak light current density at 50 V using 1 W/cm2 light intensity (A/cm2) | Peak dark current density at 50 V (A/cm2) | Photo to dark current density ratio (PDCDR) |
|---|---|---|---|---|---|
| Equal finger width and spacing designs (S = W) | 2-Fingers | W = S = 13.33 | 1e06 | 3.8e-10 | 3e15 |
| 3-Fingers | W = S = 8.0 | 1.8e06 | 1.73e-10 | 1e16 | |
| 4-Fingers | W = S = 5.71 | 4.63e06 | 1.13e-10 | 4.1e16 | |
| 5-Fingers | W = S = 4.44 | 3.88e06 | 6.75e-10 | 6e15 | |
| 6-Fingers | W = S = 3.63 | 8e06 | 1.2e-10 | 6.6e16 | |
| Double finger spacing designs (S = 2W) | 2-Fingers | W = 10.0 S = 20.0 | 6.4e05 | 1.1e-10 | 5.8e15 |
| 3-Fingers | W = 5.7 S = 11.4 | 1.2e06 | 2.2e-09 | 5e14 | |
| 4-Fingers | W = 4.0 S = 8.0 | 3.4e06 | 1.23e-10 | 2.7e16 | |
| 5-Fingers W = 3.07 | S = 6.14 | 2.6e06 | 9.5e-11 | 3e16 | |
| 6-Fingers | W = 2.5 S = 5.0 | 6.4e06 | 3.38e-10 | 1.9e16 |