Comparative Study of Heterosturcture Barrier Diodes in the GaAs/AlGaAs System

Peer reviewedPublisher PD

Extracting random numbers from quantum tunnelling through a single diode

Random number generation is crucial in many aspects of everyday life, as online security and privacy depend ultimately on the quality of random numbers. Many current implementations are based on pseudo-random number generators, but information security requires true random numbers for sensitive applications like key generation in banking, defence or even social media. True random number generators are systems whose outputs cannot be determined, even if their internal structure and response history are known. Sources of quantum noise are thus ideal for this application due to their intrinsic uncertainty. In this work, we propose using resonant tunnelling diodes as practical true random number generators based on a quantum mechanical effect. The output of the proposed devices can be directly used as a random stream of bits or can be further distilled using randomness extraction algorithms, depending on the application

Atomic-scale authentication with resonant tunneling diodes

The room temperature electronic characteristics of resonant tunneling diodes (RTDs) containing AlAs/InGaAs quantum wells are studied. Differences in the peak current and voltages, associated with device-to-device variations in the structure and width of the quantum well are analyzed. A method to use these differences between devices is introduced and shown to uniquely identify each of the individual devices under test. This investigation shows that quantum confinement in RTDs allows them to operate as physical unclonable functions

Thermal Stability of Beryllium Doped InP/InGaAs Single and Double HBTs Grown by Solid Source Molecular Beam Epitaxy

Heavily Beryllium doped (~1.5 ×10 19 cm -3 ) InP/InGaAs single heterojunction bipolar transistors (SHBTs) and double heterojunction bipolar transistors (DHBTs) have been successfully grown by solid source molecular beam epitaxy (SSMBE). The epitaxial growth was performed on a VG 90H MBE system with 100mm wafer growth capability. The novelty of this process was the use of dimeric phosphorus generated from a gallium phosphide (GaP) decomposition source which permitted growth at fairly low temperature (420 o C) while conserving extremely high quality materials. Thermal stability studies were then performed on the heavily doped HBTs using postgrowth annealing in an N2 ambient. The devices were annealed over a temperature range of 350-550 o C for 15 minutes prior to fabrication. The relatively low growth temperature of ~420 o C and the use of stoichiometric conditions for both the arsenides and phosphide materials produced remarkably thermally stable, high-gain SHBTs and DHBTs up to annealing temperatures of 550 o

An inter-subband device with terahertz applications

A theoretical analysis of a modulator based on two coupled resonators is presented in this paper. This modulator exhibits a resonant enhancement in its response. It is used as a component of tunneling structures designed for operation at terahertz frequencies; unlike conventional resonant tunneling structures, these use triple barriers. Data from optical and electrical measurements on a series of devices based on one design of a triple-barrier tunneling structure have been analyzed to estimate their behavior at frequencies over 1 THz. The analysis gives values for the resonantly enhanced admittance, its bandwidth, the bias-frequency relationship, and the requirements for a matching circuit to a 50-Ω environment. The results show that one existing structure might be used in oscillators working at 1 THz

Strong PUFs from arrays of resonant tunnelling diodes

In this work, we design and implement a strong physical uncloneable function from an array of individual resonant tunnelling diodes that were previously described to have a unique response when challenged. The system demonstrates the exponential scalability of its responses when compared to the number of devices present in the system, with an expected large set of responses while retaining a 1:1 relationship with challenges. Using a relatively small set of 16 devices, 256 responses are shown to have promising levels of distinctness and repeatability through multiple measurements

Quantum authentication

In secure communication, users must have a method of authenticating the identity of the recipients of their data, and vice versa. This requires the capability of generating a unique yet reproducible signature under a variety of environmental conditions. At present, these unique signatures are widely generated by Physically Unclonable Functions, or PUFs, which use physical characteristics of specific structures containing inherent randomness due to their manufacturing process. These hard to predict physical responses are quantised to generate a unique identity which can be used for authentication. However, these devices are size-limited by their classical design, posing challenges to microelectronic implementation. Here we show that the extensively studied and problematic fluctuations in the current-voltage measurements of Resonant Tunnelling Diodes (RTDs) can be reapplied to function as a PUF without conventional size limitations. This is possible due to quantum-mechanical tunnelling within the RTD, and, on account of these room temperature quantum effects, we term such devices QUFs – Quantum Unclonable Functions. When stimulated with a range of voltages, these devices produce a range of current outputs whilst exhibiting characteristic negative differential resistance in the region where resonant tunnelling takes place. The resultant current-voltage spectra are dependent on the exact atomic structure and composition of the quantum well within the RTD, and so are unique to the device in question. This allows us to create ‘PUF-like’ devices at the on-chip scale which explicitly make use of room-temperature quantum phenomena and subsequently provides a path towards resource-low quantum authentication protocols