Oscillation and Photoresponse of High-Resistivity <i>n</i>-GaAs Diodes

Torrens, A. B.; Young, L.

doi:10.1139/p72-152

Cited by 2 publications

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“…However, no report has been made of any occurrence of either negative transients or of low-frequency oscillations in InP. However, oscillations have been observed in GaAs by Torrens and Young (37). Kaminska et ai.…”

Section: Thus the Defect Concentrations Followmentioning

confidence: 99%

Optical Transient Current Spectroscopy of Deep Levels in Semi‐Insulating Indium Phosphide

Backhouse

Young

1991

J. Electrochem. Soc.

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Deep levels in iron-compensated semi-insulating InP were investigated by a form of digital optical transient current spectroscopy (OTCS). The decay of the transient photocurrent following periods of illumination was analyzed by a numerical method not previously applied to the problem. This could resolve a transient into a sum of exponential decays with time constants spanning a range of 104. Each time constant corresponds to the release of electrons or holes from a particular deep level. The temperature dependence gave information on the activation energy of the corresponding deep levels. By digitizing the entire transient, rather than recording two points, or their difference, as in the original OTCS method, only one sweep of temperature is required. Since the present algorithm determines the amplitudes and time constants of the exponential decays simultaneously, base-line induced artifacts and related problems encountered in previous work are avoided. The temperature range was limited by excessive dark current above about 340 K, and by "negative transients" and low-frequency oscillations below about 260 K. In the accessible range, nine deep levels were resolved. One level, previously unobserved in any type of InP, may be due to phosphorus vacancies. Of the remaining eight levels, one had previously been identified by OTCS in semi-insulating InP. The remaining seven had not previously been detected in semi-insulating InP but had activation energies close to levels previously found using capacitance deep level spectroscopy in doped (i.e., conducting) material. "Negative transients" are defined as transients in which the current initially undershoots the steady-state value. Low frequency oscillations were observed in the same range of temperature, depending upon the applied voltage. It is tentatively proposed that a dependence on voltage of both positive and negative transients and of the low-frequency oscillations arises from field-enhanced trapping. The oscillations are attributed to traveling highfield domains caused by hot-electron trapping following the original Ridley model. InP has the same advantages that GaAs has over Si, that is, high electron mobility, direct bandgap and semiinsulating substrates while offering more promise of low surface-state interfaces, thus making an insulated-gate field-effect transistor more feasible (1). InP is the appropriate substrate of opto-electronic devices based on epitaxial layers of lattice-matched Inl_=Ga~syPl-~ and a successful n-channel metal oxide semiconductor (NMOS) technology would allow optical components and transistors to be built upon the same substrate (2, 3). A problem so far with the InP NMOS technology is that the drain current of InP insulated-gate field-effect transistors has been reported to drift with time by 10 or even 90% (1, 4). Deep levels, a source of this drift, could be present in the starting material, as received from the crystal grower, or could be introduced by device fabrication. The aim of the present work was to investigate deep levels pr...

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Section: Thus the Defect Concentrations Followmentioning

confidence: 99%