Separative extended-gate AlGaAs/GaAs HEMT biosensors based on capacitance change strategy

Separative extended-gate AlGaAs/GaAs high electron mobility transistor (HEMT) biosensors based on the capacitance change strategy are proposed and fabricated. The working mechanism underlying this strategy is clearly clarified via examining the capacitance evolution on biorecognition and the capacitance matching issue between the HEMT and the sensing pad. The fabricated biosensors demonstrate a good linear current/voltage response to a label-free prostate-specific antigen (PSA) target over a broad concentration range of 100 fg/ml to 10 ng/ml in both 0.1× and 1× phosphate buffered saline solutions. Specifically, the sensitivity variation approaches 8.7% dec^-1 at the critical concentration level of 2-8 ng/ml that enters the normal PSA region in the human body. The advantages of high sensitivity, low-cost, and convenience of usage make the proposed HEMT biosensors potential candidates for prostate cancer diagnosis.