Design and Evaluation of Graphene-Silicon Heterojunction LEDs for Breast Cancer Detection

Breast Cancer remains a devastating affliction for humanity, particularly due to its low survival rates, especially when detected at advanced stages and metastasis has occurred. Early diagnosis is crucial to increase survival rates, but current diagnostic techniques such as mammography and MRI are costly and require an experienced radiologist to interpret results. Transillumination is a non-invasive diagnostic technique that uses light to detect breast abnormalities. LEDs are important in transillumination as the illumination pattern can show abnormalities in breast tissues. Graphene-based materials offer a promising avenue for the creation of thin, flexible, and durable two-dimensional (2-D) light-emitting sources. At the same time, the exceptionally high carrier mobility of graphene ($\sim 15000 \frac{\text{cm}^{2}}{V \sec }$) and low band gap in graphene/Si heterojunction LEDs enhances the performance of such LEDs resulting in lower resistance, improved electron-hole recombination, high external quantum efficiency as compared to the traditional GaAs ($\sim 4000 \frac{\text{cm}^{2}}{V \sec }$) and AlGaAs ($\sim 212 \frac{\text{cm}^{2}}{V \sec }$) LEDs. Hence, the present work explores the potential use of a graphene/silicon hetero junction LED in breast cancer diagnosis. At 690 nm Graphene/Silicon hetero junction LED has a responsivity of $285 \frac{\rm mA}{\rm W}$ whereas responsivity of $0.6 \frac {\rm{\mu A}}{\rm{W}}$ and $0.9\frac {\rm{\mu A}} {\rm{W}}$ were obtained in the AlGaAs and GaAs LEDs. The present study also investigates the effect of light penetration on breast tissues, including temperature-dependent absorptivity, using the designed LED. The internal quantum efficiency of the proposed LED is also found to be around 37.5% as compared to 24% and 27% for AlGaAs and GaAs LEDs. Thus, the development of such low-cost, radiation-free, and efficient diagnostic optoelectronic devices for breast cancer could significantly increase survival rates, especially in developing countries where access to expensive diagnostic techniques is limited.