Resonant tunnelling diode
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A resonant tunnel diode (RTD) is a device using the quantum effect and the negative differential resistance (NDR). The RTD is one of devices generating a terahertz wave at room temperature. The application which has a ultra high-speed is easy to constitute a device and a circuit with the RTD. Therefore, The RTD is extensively studied.
The structure of the RTD is a single quantum well structure surrounded by very thin layer barriers. This structure is called a double barrier structure. Carriers such as an electron and a hole can only have discrete energy values inside the quantum well. When a voltage is placed across the RTD, the terahertz wave emits. This is the reason that the energy value inside the quantum well is equal to the emitter side energy. A voltage is placed more, the terahertz stop emitting. Because the energy value in the quantum well is outside the emitter side energy.
This structure can be grown to by molecular beam heteroepitaxy. GaAs and AlAs particularly are used to form this structure. AlAs/InGaAs or InAlAs/InGaAs can be used.
