  We present a comprehensive electrical characterization of an InAs/InP
nanowire heterostructure, comprising two InP barriers forming a quantum dot
(QD), two adjacent lead segments (LSs) and two metallic contacts, and
demonstrate how to extract valuable quantitative information of the QD. The QD
shows very regular Coulomb blockade (CB) resonances over a large gate voltage
range. By analyzing the resonance line shapes, we map the evolution of the
tunnel couplings from the few to the many electron regime, with electrically
tunable tunnel couplings from <1 ${\mu}$eV to >600 ${\mu}$eV, and a transition
from the temperature to the lifetime broadened regime. The InP segments form
tunnel barriers with almost fully symmetric tunnel couplings and a barrier
height of ~350 meV. All of these findings can be understood in great detail
based on the deterministic material composition and geometry. Our results
demonstrate that integrated InAs/InP QDs provide a promising platform for
electron tunneling spectroscopy in InAs nanowires, which can readily be
contacted by a variety of superconducting materials to investigate subgap
states in proximitized NW regions, or be used to characterize thermoelectric
nanoscale devices in the quantum regime.
