Aluminium Arsenide (AiAs)

• The manufacturing process of aluminum arsenide material

High purity aluminum (AL) and arsenic (AS) are purified by regional smelting or chemical purification, with a purity requirement of 99.9999% (6N) or more.

Synthesis of ALAS polycrystal: AL and AS are mixed in stoichiometric ratio, and ALAS powder is generated by solid phase reaction or gas phase synthesis at high temperature (about 1200℃).

Gas phase deposition: ALAS films are generated by chemical vapor deposition (CVD) or molecular beam epitaxy (MBE)

2. Crystal growth

Molecular beam epitaxy (MBE): In an ultra-high vacuum environment, high quality single crystal thin films are grown layer by layer on the substrate (1GAAS, SIC) by electron beam evaporation of AL and AS atoms.

Metal organic chemical vapor deposition (MOCVD): Using trimethyl aluminum (TMAL) and arsenic alkane (ASH₃) as precursors, ALAS films are deposited at high temperature (600-900℃), which is suitable for the preparation of high performance optoelectronic devices

Vertical gradient solidification (VGF) method: used for growing large size ALAS single crystal ingot, suitable for substrate material preparation.

3. Post-treatment process

Doping control: N-type or P-type conduction is achieved by injecting silicon (SI) or carbon (C).

Heterojunction preparation: high performance device structure is formed by combining with GAAS, INGAAS and other materials.

Surface treatment: Chemical mechanical polishing (CMP) improves surface flatness to meet the requirements of nanoscale devices.

• qualification

1. Excellent semiconductor performance

Band gap width: 2.13 EV (22℃), between silicon (1.1 EV) and gallium nitride (3.4 EV), suitable for high frequency, high temperature device applications.

Lattice matching: The lattice constant of ALAS is close to that of GAAS (ALAS is 5.66 A, GAAS is 5.65 A), which can realize high quality hetero junction epitaxial growth and reduce interface defects.

2. High dielectric constant and thermal stability

The dielectric constant is 10.3, which is suitable for the design of insulation layer of high frequency microwave devices and integrated circuits.

The melting point is up to 1740°C, and the chemical stability is excellent in high temperature environment. It is suitable for high temperature electronic devices and corrosion resistant coatings.

3. Outstanding optical performance

In optoelectronic devices, ALAS/GAAS multilayer films can form high reflectivity BRAGG mirrors, which are widely used in lasers and photodetectors.

The ALO_X layer generated by wet nitrogen oxidation has the characteristics of low refractive index, which improves the light limiting ability of VCSEL and reduces the threshold current.

4. Low material consumption and environmental protection

The material utilization rate of thin film preparation process (such as MOVPE) is high, and the material cost per unit device is lower than that of traditional bulk material process.

The wet nitrogen oxidation process has no harmful by-products and is in line with the trend of green manufacturing

• Comparative advantages with other materials

| metric               | ALAS                      | GAAS                     | SIC

| band gap (EV)         2.16 (direct)              1.42 (direct)              3.3 (indirect)

| Electron mobility (CM²/V·S) | 800 (300K)           | 8500（300K）              | 400（300K）

| Thermal conductivity (W/CM·K) | 0.5                       | 0.46                      | 4.9

| Maximum operating temperature (℃) |> 500                      | 300                       | >600

| Electric field penetration (V/CM) | 4 x 10⁶                    | 4×10⁶                    | 2.5×10⁶

• Industrial application of aluminum arsenide materials

1. High temperature electronic devices

High temperature resistance: the working temperature can reach more than 500℃, far exceeding silicon (<150℃) and GAAS (<300℃), suitable for aerospace, oil exploration and other extreme environments.

High breakdown field: about 4 x 10⁶ V/CM, suitable for high voltage power electronic devices (such as thyristor, IGBT).

High thermal conductivity: ~0.5 W/CM·K, better than GAAS (0.46 W/CM·K), high heat dissipation efficiency.

2. Photoelectric devices

Ultraviolet detector: sensitive to 200-400 NM ultraviolet light, fast response (sub-nanosecond), used for flame monitoring, ozone detection.

Laser diode: efficient light emission in the near-infrared band (850-900 NM) combined with GAAS to make vertical cavity surface emitting laser (VCSEL).

Solar cell window layer: as a anti-reflective layer to improve the efficiency of GAAS based laminated cells.

3. Semiconductor heterostructure

Lattice matching: with a mismatch rate of only 0.12% with GAAS, high quality heterojunctions (such as ALAS/GAAS) can be formed for high frequency transistors (HEMT, HBT).

Electronic limit layer: The high band gap ALAS layer can effectively limit the carrier and improve the device gain and frequency response.

4. Sensors and MEMS

Pressure sensor: high elastic modulus (~250 GPA) and low thermal expansion coefficient (5.2 x 10-⁶/℃), suitable for high precision pressure measurement.

Microelectromechanical systems (MEMS): used as high temperature resistant structural materials for automotive engine sensors

• Challenges and Development Trends

1. Material brittleness: ALAS has high hardness but poor ductility, so the substrate processing process needs to be optimized.
2. Preparation cost: the growth of high quality single crystal is difficult and the cost is higher than GAAS.
3. Emerging directions: Heterojunction integration: high frequency and high voltage devices are developed in combination with INALAS and GAN; nanostructures: quantum dots and nanowires improve the efficiency of optoelectronic devices.

As a wide band gap semiconductor material, ALAS has irreplaceable advantages in high temperature electronics, photoelectric detection and heterojunction devices. Its potential in extreme environment applications is driving technological breakthroughs, and it is expected to achieve large-scale application in energy, aerospace and sensor fields in the future, and its market potential will be further released.