Capacitive infrared photodetector comprising a quantum dot layer

A photodetector device comprising:

• an n-type quantum dot layer in a semiconductor heterostructure, the quantum dot layer comprising a plurality of quantum dots embedded within an n-type semiconductor host, an energy gap between valence and conduction bands of the quantum dot layer being smaller than an energy gap between valence and conduction bands of the semiconductor host;
• the n-type semiconductor host being n-doped to a doping density approximately equal to a density of the quantum dots embedded in the host such that a fundamental energy level of the semiconductor host is filled with electrons;
• wherein electrons within the quantum dot layer are excited upon an application of a negative electrical bias to the device and are trapped within confined states in the quantum dots, the device having a first capacitance ε/W′ at a time t1 as a result of the presence of the trapped electrons, where ε is an average dielectric permittivity of materials used in the photodetector and W′ is a space charge region of the device after the application of the electrical bias;
• and
• wherein upon an illumination of the device by light having a photon energy at least equal to a difference between an energy of the confined electrons and a conduction band energy in the quantum dot layer, a plurality of the trapped electrons are excited into a conduction band of the quantum dot layer, the device having a second capacitance ε/W″ at a time t2 as a result of the excitement of the trapped electrons, where W″ is a space charge region of the device after excitation of the plurality of the trapped electrons into the conduction band;
• wherein a difference between ε/W″ and ε/W′ is indicative of an incidence of the light on the device.