BEOL‐Compatible 4F² Oscillator Using Vertical InGaAs Biristor for Highly Scalable Monolithic 3D Ising Solver

Abstract

Ising solvers are important for efficiently addressing non‐deterministic polynomial‐time (NP)‐hard combinatorial optimization problems (COPs), where scalability and compactness are crucial for practical applications. In this study, an experimental demonstration of an oscillator‐based Ising solver employing a highly scalable 4F2 InGaAs bi‐stable resistor (biristor) is presented. It is first explored the oscillation behavior of the InGaAs biristor, establishing that classical Ising spins can be emulated using the sub‐harmonic injection locking (SHIL) technique. Furthermore, capacitive and resistive coupling between two coupled InGaAs biristors is demonstrated, leading to out‐of‐phase and in‐phase coupling, respectively. Employing this foundational technology, it is experimentally achieved a solution to the MaxCUT problem with the InGaAs biristor‐based Ising solver, supplemented by simulation‐based behavior evaluations. This emerging device architecture offers a viable pathway to surmount the scaling limitations faced by present hardware‐based Ising solvers, representing a significant step forward in the development of efficient, scalable solutions for complex optimization challenges.