High gain-bandwidth product Ge/Si tunneling avalanche photodiode with high-frequency tunneling effect

This study presents a theoretical investigation of a novel Ge/Si tunneling avalanche photodiode（TAPD）with an ultra-thin barrier layer between the absorption and p＋ contact layer. A high-frequency tunneling effect is introduced into the structure of the barrier layer to increase the high-frequency response when frequency is larger than 0.1 GHz, and the-3 dB bandwidth of the device increases evidently. The results demonstrate that the avalanche gain and-3 dB bandwidth of the TAPD can be influenced by the thickness and bandgap of the barrier layer.When the barrier thickness is 2 nm and the bandgap is 4.5 eV, the avalanche gain loss is negligible and the gainbandwidth product of the TAPD is 286 GHz, which is 18% higher than that of an avalanche photodiode without a barrier layer. The total noise in the TAPD was an order of magnitude smaller than that in APD without barrier layer.

Avalanche-enhanced photocurrents in pin silicon waveguides at 1550 nm wavelength

The photocurrent effect in pin silicon waveguides at 1550 nm wavelength is experimentally investigated. The photocurrent is mainly attributed to surface-state absorption,defect-state absorption and/or two-photon absorption.Experimental results show that the photocurrent is enhanced by the avalanche effect.A pin silicon waveguide with an intrinsic region width of 3.4μm and a length of 2000μm achieves a responsivity of 4.6 mA/W and an avalanche multiplication factor of about five.

RBFK cipher:a randomized butterfly architecture‑based lightweight block cipher for IoT devices in the edge computing environment

Internet security has become a major concern with the growing use of the Internet of Things(IoT)and edge computing technologies.Even though data processing is handled by the edge server,sensitive data is generated and stored by the IoT devices,which are subject to attack.Since most IoT devices have limited resources,standard security algorithms such as AES,DES,and RSA hamper their ability to run properly.In this paper,a lightweight symmetric key cipher termed randomized butterfly architecture of fast Fourier transform for key(RBFK)cipher is proposed for resource-constrained IoT devices in the edge computing environment.The butterfly architecture is used in the key scheduling system to produce strong round keys for five rounds of the encryption method.The RBFK cipher has two key sizes:64 and 128 bits,with a block size of 64 bits.The RBFK ciphers have a larger avalanche effect due to the butterfly architecture ensuring strong security.The proposed cipher satisfies the Shannon characteristics of confusion and diffusion.The memory usage and execution cycle of the RBFK cipher are assessed using the fair evaluation of the lightweight cryptographic systems(FELICS)tool.The proposed ciphers were also implemented using MATLAB 2021a to test key sensitivity by analyzing the histogram,correlation graph,and entropy of encrypted and decrypted images.Since the RBFK ciphers with minimal computational complexity provide better security than recently proposed competing ciphers,these are suitable for IoT devices in an edge computing environment.

A Novel Key Scheduling Scheme for AES Algorithm

This paper examines the theory of AES key scheduling and its potential problems.We propose a novel key scheduling scheme.The scheme improves the speed of key expansion without increasing computational complexity,reduces the dependency of output key on input key during key expansion,and improves the avalanche effect of key expansion.