Исследованы электрические и низкочастотные шумовые характеристики одиночных фотодиодных гетероструктур p-InAsSbP/n-InAs, выращенных на подложках n + -InAs и помещенных в атмосферу, содержащую пары этанола. Выявлены взаимосвязи значения сопротивления гетероструктур и спектральной плотности токового шума с насыщенностью воздуха парами этанола и рассмотрены возможные причины такой взаимосвязи. Ключевые слова: InAs-фотодиоды, датчики углеводородов, низкочастотный шум, природный окисел на поверхности InAs, поверхностно-чувствительные структуры.

The frequency and current dependences of the optical output spectral noise density, Slph, in p-InAsSbP/n-InAs infrared light emitting diodes (LEDs) has been measured for the first time. LEDs with emission centered at wavelengths  = 2.8 and 3.5 µm have been studied. In both cases, in the frequency range 2 ≤ f ≤ 100 Hz the noise spectrum is 1/f like. At constant LED pumping current, Slph is proportional to the photocurrent squared (~ Iph2). The 1/f noise intensity Slph for the LED with emission centered at  = 2.8 µm is ~2 times higher. In the LED pumping current range 0.02  ILED  0.1 A (60  jLED  300 A/cm2) the optical output 1/f noise is practically independent of ILED. The intensity of the LEDs’ optical output 1/f noise is less than the intensity of the photodiode reverse bias current noise by ~4 orders of magnitude.

The terahertz absorption spectra of sodium magnesium chlorophyllin (Chl-Mg-Na) and sodium copper chlorophyllin (Cu-Chl), two major members of the chlorophyll derivative family, have been measured in the range 0.2−2.5 THz, at room temperature. The capability of terahertz spectroscopy for quantitative characterization of Chl-Mg-Na intermolecular vibrations was investigated and the sensitivity of transitions with degree of hydration by changes in the molecular environment was examined. For the Cu-Chl derivative, a broad feature was observed around 1.8 THz which currently hinders clear Cu-Chl identification and quantification.

Terahertz time-domain spectroscopy has been used to investigate the vibrational spectra of polycrystalline sodium magnesium chlorophyllin - one of the natural derivatives of chlorophyll - over the temperature range 88 K–298 K. A number of well-resolved absorption peaks were observed in the frequency range 0.2–2.5 THz, which are interpreted as originating from mixed character of intramolecular and intermolecular vibration modes. As the temperature is increased, the observed absorption features resolve into broader peaks. The peak centered at 1.83 THz shifts towards higher frequencies, indicating that for this feature, significant intermolecular anharmonicity exist.

Low frequency noise in P-InAsSbP/n-InAs infrared light emitting diode- photodiode pairs is investigated for the first time at 300 K. It is shown that photocurrent fluctuations under LED illumination are smaller than photocurrent fluctuations under a black body illumination. When the photodiode is illuminated by LED, the spectral noise density follows the 1/f dependence. In the case of a black body illumination we observe a significant contribution of generation-recombination noise.

Low dimensional nano-systems are promising candidates for manipulating, controlling and capturing photons with large sensitivities and low-noise. If quantum engineered to tailor the energy of the localized electrons across the desired frequency range, they can allow devising efficient quantum sensors across any frequency domain. Here, we exploit the rich few-electrons physics to develop millimeter-wave nanodetectors employing as sensing element an InAs/InAs0.3P0.7 quantum-dot nanowire, embedded in a single electron transistor. Once irradiated with light the deeply localized quantum element exhibits an extra electromotive force driven by the photothermoelectric effect, which is exploited to efficiently sense radiation at 0.6 THz with a noise equivalent power < 8 pWHz-1/2 and almost zero dark current. The achieved results open intriguing perspectives for quantum key distributions, quantum communications and quantum cryptography at terahertz frequencies.