Output buffer glow and its mitigation in H4RG-15 detectors

The Hawaii-4RG near-infrared detectors offer several output configurations in which the detectors can be interfaced with the European Southern Observatory cryogenic preamplifiers. The buffered mode of output operation has the advantages of higher speed and lower electrical crosstalk between the outputs, reduced unit cell current, etc. One of the effects of the buffered mode operation is increased glow at the bottom of the array due to the operation of the output buffers compared to the unbuffered mode. The excess glow can be a limiting source to achieve low noise in long integrations using the up-the-ramp sampling readout mode. The glow can be significantly reduced by optimally biasing the output buffer stages. This work presents the output buffer glow issue, its quantification in terms of glow per read, glow per unit integration time, its dependency on pixel speed, and its mitigation by optimization of buffered mode operation.