Flux

From Incident Beam to Net Growth

Why It Matters

Beam Flux Monitor tells you what leaves the source.

Flux tells you what actually incorporates.

Between those two lies everything that matters:

Desorption
Surface kinetics
Temperature dependence
Elemental interactions

Incident flux alone does not define growth.

Net flux does.

Incident Flux Is Only the Beginning

From BFM, you already know:

Actuator → BEP → Incident Flux (atoms / nm² / s)

But not every atom that arrives stays.

At real substrate temperatures:

Ga can desorb
In can desorb
As can re-evaporate
Nitrogen activation efficiency varies

Surface chemistry is dynamic.

Flux models this reality.

Net Flux per Element

Flux takes:

Incident atomic flux
Substrate temperature
Desorption models per species
Interaction assumptions

And computes:

Net incorporation flux per element.

Element by element.

Now you are not guessing at stoichiometry.

You are calculating it.

Species-Level Prediction

With structured net flux, you can begin predicting:

Alloy composition
Growth rate
Doping incorporation
Effective V/III ratio
Stoichiometric windows

Per element.

Not empirically.

Mechanistically.

Modelling Interactions

Once you have per-element net flux:

You can model:

Surfactant effects
Competitive incorporation
Composition gradients
Intentional doping profiles
Dynamic alloy tuning

Complex gradients become programmable.

Not trial and error.

Real-World Example

We applied this to InGaN.

Linear composition gradient.

First run.

Not luck.

Not tuning by feel.

Structured flux modeling from calibrated data.

From measurement.
From engineering.

Engineering, Not Intuition

Flux shifts growth from:

“Let’s try and see.”

To:

“We know what this actuator change will do at this temperature.”

It connects:

Control → Measurement → Surface Physics → Composition

Inside the same system.

The Philosophy

Incident beam tells you what arrives.

Net flux tells you what grows.

When you can quantify incorporation, you stop reacting to results.

You design them.

Flux turns metrology and calibration into predictive material engineering.