---
title: Hawaii-4 RG Detector for NIR Astronomy
url: https://www.emergentmind.com/topics/hawaii-4-rg-detector
type: topic
---

# Hawaii-4 RG Detector for NIR Astronomy

The Hawaii-4RG (“H4RG”) detector family comprises large-format, hybrid HgCdTe-CMOS near-infrared (NIR) imaging arrays developed for demanding astrophysical applications. With 4096 × 4096 pixels, enhanced quantum efficiency, low noise, low dark current, and resilience to environmental stresses, H4RGs underpin major missions such as MOONS and WFIRST. Key variants include the H4RG-15 (15 µm pitch) and the H4RG-10 (10 µm pitch), both configurable for 2.5 μm cut-off, with bespoke cryogenic readout electronics and advanced correction pipelines. Their architecture and performance represent the state-of-the-art in NIR scientific detectors, enabling deep multi-object spectrographs and high-precision exoplanet and cosmological surveys [2012.08183][2005.00505][1908.11429].

## 1. Detector Architecture and Key Design Features

H4RG detectors utilize a substrate-removed HgCdTe photodiode array hybridized (via indium bump-bonding) to a 64-channel (H4RG-15) or 32-channel (H4RG-10) CMOS readout integrated circuit (ROIC). The H4RG-15 has a 15 µm pixel pitch (61 mm × 61 mm die), while the H4RG-10 uses 10 µm pixels. The active material bandgap is compositionally tuned for a 2.5 µm cut-off wavelength. Each pixel incorporates a source-follower amplifier and multiplexing circuitry.

The detectors implement both unbuffered (“science”) and buffered (“low-Z”) output configurations. In unbuffered mode, 32 outputs with high impedance ($Z_\text{out}\sim100$–$200\,\mathrm{k}\Omega$) are used; in buffered mode, 64 outputs with an additional on-chip source-follower reduce $Z_\text{out}$ to $<1\,\mathrm{k}\Omega$. The buffered configuration utilizes a novel, miniaturized cryogenic differential preamplifier assembly with quad ultra-low-noise CMOS amplifiers (e.g., Texas Instruments OPA4192) and Vdda pull-up topology, optimized for <50 × 50 mm² footprint to suit the constrained optical environment of fast Schmidt camera designs [2012.08183].

## 2. Electro-Optical Performance Metrics

Operational performance is characterized at temperatures from 40–100 K. Key parameters are summarized below:

| Metric                | H4RG-15 Value         | H4RG-10 Value      |
|-----------------------|----------------------|--------------------|
| Pixel pitch           | 15 µm                | 10 µm              |
| Array size            | 4096×4096            | 4096×4096          |
| Cut-off wavelength    | 2.5 µm               | 2.5 µm             |
| Full-well capacity    | >70 ke⁻              | ~100 ke⁻           |
| Read noise (CDS)      | 13 e⁻ rms            | 12 e⁻ rms          |
| UTR-128 noise         | 4.5 e⁻ rms           | 7 e⁻ rms           |
| Dark current (80 K)   | 0.009 e⁻/s/pix       | <0.01 e⁻/s/pix     |
| Quantum efficiency    | ~90% (J,H)           | 86–96% (median 91%)|
| Inter-pixel cap.      | 0.8–1.4% (rows)      | 1.8–2.6% (4-nn sum)|
| Crosstalk (buf/unbuf) | <0.01% / ~0.1%       | n/a                |

In both devices, quantum efficiency exceeds 90% through J and H bands. For the H4RG-15, the read noise remains at 13 e⁻ rms (CDS) and drops to <3 e⁻ rms in Fowler-8 sampling. The UTR-128 slope-fitting method yields ~4.5–7 e⁻ rms total noise, with marginally higher values in longer up-the-ramp (UTR) sampling due to charge injection and glow. Dark current at 40 K is 0.004 e⁻/s/pix for good pixels; hot-pixel operability improves from 92% (90 K) to 99% (40 K). For the H4RG-10 at 100 K, median dark current is 0.002 e⁻/s/pix.

## 3. Noise Sources, Persistence, and Correction Strategies

Noise in H4RG detectors comprises white (Johnson and shot), pink ($1/f$), alternating column, and picture frame noise. The overall read noise per pixel is described as:
$$
\sigma_\text{read}^2 = \sigma_w^2 + \sigma_\text{p,corr}^2 + \sigma_\text{p,uncorr}^2 + \sigma_\text{acn}^2 + \sigma_\text{pf}^2
$$
where each term corresponds to a distinct physical noise source [1908.11429].

Persistence, modeled as a multi-exponential trap population, is parameterized via:
$$
P(t) = \sum_i A_i \exp(-t/\tau_i)
$$
Fitting to SRH kinetics yields a trap activation energy $E_\text{trap}\approx0.13\pm0.01\,\mathrm{eV}$, with persistence peaking at 55–70 K and minimized ($<1\%$ full-well) at $T\leq50$ K or $T\geq80$ K [2012.08183]. Data pipelines utilize per-pixel trap-density maps and on-the-fly subtraction to correct for persistence based on measured exposure history.

Nonlinear pixel response is corrected empirically using cubic fits ($f_\text{corr}=f_\text{meas}+c_2f_\text{meas}^2+c_3f_\text{meas}^3$), removing nonlinearity effects critical for precise photometry and Doppler spectroscopy [1908.11429].

## 4. Readout Modes, Programming, and Operational Features

Both unbuffered and buffered readout configurations are available. In unbuffered mode, high output impedance results in capacitive crosstalk (∼0.1%) and row droop (up to 0.5% at ¾ full-well); buffered output with the custom cryogenic preamplifier reduces crosstalk below 0.01% and supports faster pixel clocks (up to 300 kHz/output) with no noise penalty [2012.08183]. The “Current-Boost” enable stabilizes unbuffered outputs, and direct programming of on-chip registers (notably “Register-1”) is mandatory to achieve full well and conversion gain. Enhanced-Clocking Mode is not recommended for scientific data due to column offsets.

Management of photo-emission defects (PEDs) is achieved by row-skip and substitution; column de-select alone is counterproductive. The column-deselect and row-skipping features reduce the impact of local emission artifacts. Detailed programming and calibration, including careful use of reference pixels, are critical to maintaining optimal detector performance.

## 5. Charge Injection, Inter-Pixel Capacitance, and Data Calibration

Charge injection per read is minor but spatially variable: for H4RG-15, the center region yields ~0.03 e⁻/read while edges near bond pads can reach 0.65 e⁻/read. Recommendation is to keep UTR reads at ≤128 to limit glow noise.

Inter-pixel capacitance (IPC) is characterized by nearest-neighbor coupling of 0.8–1.4% (rows) and 0.5% (columns) in the H4RG-15 and 1.8–2.6% four-neighbor sum for H4RG-10 [2005.00505]. IPC induces PSF broadening and must be corrected in high-precision applications. IPC kernels are measured directly using single-pixel reset and X-ray events and show modest spatial variation and a systematic gradient towards device edges. Data pipelines apply cross-talk corrections ($\lesssim1\%$) to maintain photometric and spectroscopic fidelity.

## 6. Environmental Qualification, System-Level Impact, and Applications

H4RG detectors have undergone rigorous environmental qualification including: 40 thermal cycles between 295–100 K, GEVS-level sine/random vibration, acoustic testing, and proton irradiation. H4RG-10 arrays retain >99% pixel operability and exhibit minimal performance drift post-exposure: hot pixels increase by ~3.5%, dark current rises negligibly (from 0.003 to 0.012 e⁻/s), and noise increment occurs in <8% of pixels (but remains within specification) [2005.00505]. The arrays are rated at TRL-6 for mission deployment.

At the system level, the product of high QE, low dark current, and low noise yields the deep imaging (e.g., $\mu_\mathrm{AB}>26$), precise spectroscopic, and photometric capabilities required for modern NIR surveys and spectrographs (e.g., MOONS for VLT, WFIRST for cosmology and exoplanet searches) [2012.08183][2005.00505][1908.11429]. Data calibration pipelines are equipped to handle nonlinearity, persistence, IPC, and noise characterization, critical for minimized error budgets in high-precision Doppler velocity measurements (e.g., exoplanet radial velocities down to $0.5$–$1.0\,\mathrm{m/s}$ uncertainties with sub-$1\,\mathrm{m/s}$ individual exposure precision) [1908.11429].

## 7. Summary Table of H4RG Key Parameters

| Characteristic                | H4RG-15              | H4RG-10               |
|-------------------------------|----------------------|-----------------------|
| Pixel count                   | 4096 × 4096          | 4096 × 4096           |
| Pixel pitch                   | 15 µm                | 10 µm                 |
| Cut-off wavelength            | 2.5 µm               | 2.5 µm                |
| Detector material             | HgCdTe, sub-rmvd     | HgCdTe, sub-rmvd      |
| Full-well (typical)           | >70 ke⁻              | ~100 ke⁻              |
| Read noise (CDS)              | ~13 e⁻               | ~12 e⁻                |
| UTR slope fit noise           | ~4.5 e⁻ (UTR-128)    | ~7 e⁻ (55 ramp)       |
| Dark current (good pixels)    | 0.009 e⁻/s/pix @ 80 K| <0.01 e⁻/s/pix @ 100 K|
| Quantum efficiency            | ∼90%                 | 86–96% (median 91%)   |
| Inter-pixel capacitance (IPC) | 0.8–1.4% rows,       | 1.8–2.6% (4 neighbors)|
|                               | 0.5% cols            |                       |
| Crosstalk (buffered/unbuf)    | <0.01% / ~0.1%       | n/a                   |

These characteristics are central to the performance envelope for high-stability NIR imaging and spectroscopy applications, with system calibration and data processing methods in place to fully exploit their scientific capabilities [2012.08183][2005.00505][1908.11429].

Source: https://www.emergentmind.com/topics/hawaii-4-rg-detector