J. Eur. Opt. Society-Rapid Publ. 22, 39( 2026) 387
Table 3. Performance comparison of the proposed nBn photodetector with reported InGaAs-based photodetector.
In this work, an InGaAs-based nBn photodetector incorporating an Al 0. 57 Ga 0. 43 As barrier layer was systematically designed and numerically analyzed using SILVACO ATLAS. Through detailed band alignment engineering, the optimal barrier composition was identified to achieve a near-zero valence band offset( DE v 35 meV) while maintaining a sufficiently large conduction band offset( DE? 1.26 eV). This configuration effectively enables barrier-free transport of minority carriers while strongly suppressing majority-carrier leakage, addressing one of the fundamental limitations of conventional InGaAs photodiodes. The optimized device demonstrates ultra-low dark current on the order of 1 pA at low reverse bias( �0.3 V), representing orders-of-magnitude improvement compared to previously reported nBn-InGaAs structures. This significant reduction is primarily attributed to the suppression of Shockley – Read – Hall generation and diffusion-related leakage mechanisms, as confirmed by current component analysis. At higher biases, the controlled contribution of tunneling current further verifies the effectiveness of the barrier design in limiting field-assisted leakage. In addition to its low-noise performance, the proposed structure maintains competitive optical characteristics. By inte-
Device |
Dark current |
Responsivity |
EQE |
Ref |
nBn- InGaAs |
̴1 pA( V r = 0.3 V, / = 300 lm) |
0.824 A / W( k = 1.55 lm, V r = 0.3 V) |
– |
This work |
nBn- |
̴8 nA( V r = 0.3 V, / |
– |
% 45( k = 1.55 lm, |
[ 15 ] |
InGaAs |
= 300 lm) |
|
V r = 0.25 V) |
|
nBn- |
̴0.9 nA( V r = 0.3 V, |
|
% 80( k = 1.55 lm, V r = 0.2 V) |
[ 6 ] |
InGaAs |
/ = 300 lm) |
|
|
|
pBin- |
̴70 pA( V r = 0.3 V, |
0.62 A / W( k = 1.55 lm, V r = 0.2 V) |
– |
[ 36 ] |
InGaAs |
/ = 500 lm) |
|
|
|
pn-InGaAs |
̴10 pA( V r = 0.3 V, |
1.08 A / W( k = 1.55 lm) |
% 86( k = 1.55 lm) |
[ 37 ] |
|
/ = 300 lm) |
|
|
|
pin-InGaAs |
̴41 pA( V r = 5 V, / = 73lm) |
0.99 A / W( k = 1.55 lm, V r = 5V) |
% 79( k = 1.55 lm) |
[ 38 ] |
extraction efficiency: at the telecommunication wavelength of 1.55 lm [ 34 ], the responsivity increases by approximately 36 %, improving from 0.60 to 0.82 A / W. This improvement is consistent with the reflectance reduction achieved through AR design and confirms that minimizing front-surface optical losses directly enhances the detector’ s photonto-electron conversion capability. In the numerical simulations performed in this study, the TCAD software provides external quantum efficiency( EQE) rather than responsivity as a direct output. Therefore, the EQE values were converted to responsivity using equation( 7), enabling a direct comparison between the simulated and AR-enhanced device performance [ 35 ]. It should also be noted that the reported responsivity values correspond to conditions in which the nBn-InGaAs structure is illuminated from the backside under an incident optical power density of 0.01 W / cm 2. Backside illumination ensures that the incident photons efficiently reach the absorbing InGaAs layer without encountering additional front-side metallization losses, thereby allowing a more accurate assessment of the intrinsic photo-response. Collectively, these results verify that integrating an appropriately engineered AR coating is an effective approach for maximizing optical coupling and elevating responsivity in nBn-type infrared photodetectors.
R ¼ g q ð7Þ hf
where g is the EQE of the detector for a given wavelength, q is the electron charge, f is the frequency of the incident photons, and h is the Planck constant.
Figure 8 shows the responsivity variation with applied bias voltage, indicating that the proposed nBn design maintains high responsivity even at very low operating bias due to the minimized VBO and optimized barrier engineering. Notably, its performance approaches that of cutting-edge planar InGaAs detectors( Table 3), confirming the viability of the structure as a strong candidate for high-performance, low-power infrared photodetection.
To benchmark the proposed device, a comparison with previously reported InGaAs photodetectors is summarized in Table 3. The proposed nBn structure exhibits an ultralow dark current of 1 pA at �0.3 V, which is significantly lower than reported nBn-InGaAs devices( 0.9 – 8 nA) under similar bias conditions, corresponding to an improvement of several orders of magnitude. Compared to conventional pn junction, PIN diode, and pBin structures, which typically show dark currents in the range of 10 – 70 pA, the proposed device still demonstrates superior suppression.
The responsivity of 0.824 A / W at 1.55 lm is comparable to literature values, although slightly lower than the 1.08 A / W reported for pn-based devices. Overall, the results indicate that the proposed nBn design achieves an excellent trade-off between ultra-low dark current and competitive optical performance.
4 Conclusion