Use this semiconductor calculation for first-order device, material, fabrication, interconnect, packaging, or reliability estimates when every coefficient and unit convention is known.

Electron injection current density (A/cm^2)

Required number in A/cm^2. Electron current density injected from emitter into base.

Hole back-injection current density (A/cm^2)

Required number in A/cm^2. Hole current density back-injected from base into emitter.

The cited overview of Semiconductor device supplies background for the terminology and domain context used by this tool.^[1]

Calculate HBT emitter injection efficiency from forward electron injection and opposing hole back-injection current densities. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Injection efficiency (ratio)

Returned number in ratio. Fraction of emitter current carried by injected carriers.

• Material composition, geometry, process history, temperature, electric field, bias, interfaces, parasitics, and fitted parameter ranges can invalidate a compact semiconductor model.
• Electron injection current density must be at least 0.
• Hole back-injection current density must be at least 0.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Compare the estimate with measured process data, current device documentation, and a higher-fidelity circuit, field, thermal, quantum, or TCAD model when the decision requires it.

• BJT Common-Base Current Gain Calculator

  Compute the BJT common-base current gain alpha as the product of emitter efficiency and base transport factor.

• BJT Emitter Efficiency Calculator

  Compute the BJT emitter injection efficiency assuming equal diffusion coefficients on both sides.

• Diffusion Capacitance Calculator

  Compute the diffusion capacitance of a forward-biased diode from stored-charge lifetime and current. Formula: Cdiff [nF] = 1e9 · (τ [ns]·1e-9 · I [mA]·1e-3) / (n · Vt [V]), where Vt = k·T/q (k=1.380649e-23 J/K, q=1.602176634e-19 C). Equivalent: Cdiff [F] = τ·I/(n·Vt). Inputs: I ≥ 0 mA, τ > 0 ns, n ≥ 1 (default 1), T > 0 K (default 300 K). Output: Cdiff ≥ 0 nF. Assumes low-level injection, negligible depletion capacitance, and quasi-neutral stored charge τ·I.