Analytic band-to-trap tunneling model including band offset for heterojunction devices

Abstract

We present an analytic band-to-trap tunneling model based on the open boundary scattering approach. The new model has three major advantages: (i) It includes not only the well-known electric field effect, but more importantly, the effect of heterojunction band offset. This feature allows us to simulate both electric field and band offset enhanced carrier recombination near a heterojunction in heterostructures. (ii) Its analytic form enables straightforward implementation into a parallel Technology Computer Aided Design device and circuit simulators. (iii) The developed method can be used for any potentials which can be approximated to a good degree such that the Schrödinger equation with open boundary conditions results in piecewise analytic wave functions. Simulation results of an InGaP/GaAs heterojunction bipolar transistor (HBT) reveal that the proposed model predicts significantly increased base currents, because the tunneling of holes in the base to traps in the emitter is greatly enhanced by the emitter-base band offset. This finding, which is not captured by existing band-to-trap tunneling models, is consistent with the experimental observation for an InGaP/GaAs HBT after neutron irradiation.

Efficient Band-to-Trap Tunneling Model Including Heterojunction Band Offset

“…14. The most intriguing finding from our work is that the normalization factors are identical for the two potentials considered, and more importantly, the same normalization factor is applicable to any 1D potentials that have open BCs and lead to piecewise analytic wave functions (14). The universal normalization factor has a very simple form as given in Eq.…”

“…5 shows the DOS results for the potential shown in the left at three locations that are 5-, 10-, and 20-nm away from the step denoted by the colored dots. The black DOS curve was computed using the constant-field DOS expression (14), which depends only on the field (not on the location). As seen from the figure, the constant-field DOS is valid only for distances more than 20-nm away from the heterojunction (HJ).…”

“…To obtain an analytic DOS model for the red potential in Fig. 1(b), we propose the open boundary scattering approach (14). In this approach, we begin by first shifting potential from Fig.…”

“…For finite volume discretization, it implements the generalized Scharfetter-Gummel method by Bochev et al (17). CHARON also contains many advanced physics models, such as Fermi-Dirac statistics, thermionic emission and tunneling transport across heterojunction (14), and band-to-trap tunneling. It has been used to simulate a wide variety of devices, including diodes, bipolar junction transistors (BJTs), heterojunction bipolar transistors (HBTs), field effect transistors (MOSFETs), wide-band gap devices (e.g., GaN devices), and transition metal oxide memristors (18)(19).…”