A method to extend wavelength into middle-wavelength infrared based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector

We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified In As Sb quantum well, Ga Sb is replaced with Al Sb/Al Ga Sb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.     

Numerical and Experimental Study on the Device Geometry Dependence of Performance of Heterjunction Phototransistors

Heterojunction phototransistors(HPTs)with scaling emitters have a higher optical gain compared to HPTs with normal emitters.However,to quantitativel.y describe the relationship between the emitter-absorber area ratio(A_e/A_a)and the performance of HPTs,and to find the optimum value of A_e/A_a for the geometric structure design,we develop an analytical model for the optical gain of HPTs.Moreover,five devices with different A_e/A_a are fabricated to verify the numerical analysis result.As is expected,the measurement result is in good agreement with the analysis model,both of them confirmed that devices with a smaller A_e/A_a exhibit higher optical gain.The device with area ratio of 0.0625 has the highest optical gain,which is two orders of magnitude larger than that of the device with area ratio of 1 at 3 V.However,the dark current of the device with the area ratio of 0.0625 is forty times higher than that of the device with the area ratio of 1.By calculating the signal-to-noise ratios(SNRs) of the devices,the optimal value of Ae/Aa can be obtained to be 0.16.The device with the area ratio of0.16 has the maximum SNR.This result can be used for future design principles for high performance HPTs.