Bare Silicon Photodiode Wafer Suppliers & Exporter for Christchurch

1. Substrate Quality, Epitaxy, and Junction Architectures

Silicon photodiode bare wafers represent the primary building block of modern optoelectronic front ends. Unlike packaged plastic or TO-can encapsulated diodes, sourcing unencapsulated bare wafers (or diced dies) provides electro-optical engineers with complete autonomy over dielectric coatings, wire bonding geometries, hybrid ASIC integration, and optical path engineering. The silicon wafers exported to Christchurch's photonics cluster are grown using high-purity Float-Zone (FZ) or Czochralski (CZ) monocrystalline techniques with <100> or <111> crystal orientation, achieving exceptional dark current suppression (<1 nA/cm² at -5V bias) and carrier lifetimes exceeding 1000 µs.

Our standard offering includes SGPIN400 linear bare photocell arrays and discrete planar junction chips. A planar diffused p-n junction or intrinsic p-i-n junction is formed by selective thermal diffusion or ion implantation of boron acceptors into n-type silicon substrates. By strictly regulating the resistivity of the high-ohmic intrinsic layer (typically 2,000 to 10,000 Ω·cm), the depletion layer fully extends under modest reverse biases, minimizing junction capacitance (Cj) down to single-digit picofarads per square millimeter. This makes these bare wafers ideal for high-speed pulse response, low-noise analytical equipment, and multi-channel optical pyrometry.

2. Spectral Responsivity & Passivation Coatings

Bare photodiode wafers feature a calibrated spectral response across the 190 nm to 1100 nm window. For clients engaged in UV or VIS spectrometry, surface recombination velocity is heavily mitigated using an ultra-thin thermally grown silicon dioxide (SiO2) and silicon nitride (Si3N4) antireflective passivation stack. This AR coating is tuned to cancel destructive Fresnel reflections at designated center wavelengths (e.g., 632.8 nm, 850 nm, or 905 nm), achieving external quantum efficiencies (EQE) beyond 85%.

• Spectral Range: 350 nm – 1100 nm (Extended UV-enhanced versions down to 200 nm available on demand)
• Peak Responsivity: ≥ 0.62 A/W at 900 nm wavelength
• Dark Current Density: Typically 0.2 to 1.5 nA/cm² at Vr = 5V, 25°C
• Shunt Resistance (Rsh): ≥ 500 MΩ, guaranteeing superior signal-to-noise ratios (SNR) in transimpedance amplification stages
• Front-Side Metallization: Vacuum sputtered Aluminium-Silicon (Al-Si) or Gold (Au) bonding pads optimized for automated wedge or ball wire bonding
• Backside Contact: Gold/Chromium (Au/Cr) common anode metallization suitable for conductive epoxy die attachment or eutectic soldering