Samia Islam

Date of Award

Fall 2021

Document Type

Open Access Thesis


Electrical Engineering

First Advisor

MVS Chandrasekhar


This thesis is divided into two sections. At first, we demonstrate ~1.5x detectivity increase in AlGaN photodiodes on sapphire using distributed micropixel arrays with 5-15 µm pixel diameter. This is due to the ~10x larger chip footprint of the 5um diameter micropixel arrays compared to planar control structures with identical p contact area. The responsivity of the larger areas was the same as that of the control structure despite the larger footprint while the dark currents, an indicator of noise, remained unchanged. The photocurrent generated between pixels was collected due to transmission line effects connecting the pixels separated by 5um, rather than minority carrier diffusion alone, which would fall off at

In the second section, we have analyzed low temperature performances of these photodiodes. Measured I-Vs at different temperature (90K-300K) ranges do show some shift in turn on voltage and current magnitude. Using MATLAB, we verified two different circuit models which can correctly predict the nano pipe freeze out mechanism at lower temperatures and explained the reason behind the 4x increase of light intensity