Abstract: An analog-to-digital converter (ADC) for converting an analog signal into a digital signal includes an amplifier circuit configured to receive the analog signal, and to generate a plurality of amplifier signals by amplifying the analog signal; a comparison circuit configured to compare a plurality of voltage levels corresponding to the plurality of amplifier signals with a positive reference voltage level and a negative reference voltage level, and to output conversion target signals based on a result of the comparison; and a converter circuit configured to convert the conversion target signals into a plurality of digital signals.

Abstract: A tunnel junction structure comprises an n-type tunnel junction layer of a first semiconductor material, a p-type tunnel junction layer of a second semiconductor material and a tunnel junction between the tunnel junction layers. The first semiconductor material includes gallium (Ga), nitrogen (N), arsenic (As) and is doped with a Group VI dopant. The probability of tunneling is significantly increased, and the voltage drop across the tunnel junction is consequently decreased, by forming the tunnel junction structure of materials having a reduced difference between the valence band energy of the material of the p-type tunnel junction layer and the conduction band energy of the n-type tunnel junction layer. Doping the first semiconductor material n-type with a Group VI dopant maximizes the doping concentration in the first semiconductor material, thus further improving the probability of tunneling.