A monolithic QCL/APD IR Transceiver in which the QCL transmitter and APD receiver have the same N MQW stage composition and variation in thickness in the z direction for all positions in x and y directions. The heterostructure is configured via asymmetric stages, additional stages for the APD or by reversing the polarity of the p-n junction for the APD or a combination thereof such that the upper energy state in the QCL under forward bias is confined to the quantum well and in the APD under reverse bias is near the top of the quantum well in energy and localized in the quantum well to spatially overlap with the lower energy state to facilitate detection of echo photons. The QCL and APD may be positioned end-to-end, side-by-side or as a common region of the heterostructure.
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