Assembly and integration of optical sensors based on quantum dots-in-well in double-barrier photodetector array

We have been developing a kind of micro spectrometer with 64 pixels GaAs-based quantum dots-in-well in double barrier photodetector linear array. The novel photodetector array has a specific inner multiplication at extremely weak illumination environment at low bias voltage. High current gains are achieved and accompanied by extremely low dark currents. The photoelectric response spectrum of the photodetector shows excellent light absorption characteristics from 400nm up to 850nm. Unlike the photon sensitivity of the previous AlGaAs QD-RTD, the QDs photodetector shows high sensitivity to the light irradiation and operating at room temperature. Its current responsivity can reach about 7 × 10¹¹ A/W when 0.01 picowatts (pW) 633nm light power and -0.5V bias are added. The CTIA readout circuit has been designed to acquire the photocurrent with wide wavelength range under different radiations especially at weak light settings. Two kinds of silicon interposer, namely via-with-one-line and via-with-four-line have been simulated and compared. ADS simulations demonstrate the via-with-four-line silicon interposer is better than via-with-one-line silicon interposer and other interposers such as PCB interposer and ceramic interposers can reduce more crosstalk and suppresses noise. And the response voltage is 7mV and 80μs integration time at 300K. The voltage responsivity has reached about 2.7×10⁹ V/W. A high sensitivity spectrometer based on the photodetector array was made and mounted in a microscopy hyperspectral imaging system with optical path switcher. The system has been used to analyze and comparative study the blood smears and biological section.