Two-dimensional profiling of carriers in a buried heterostructure multi-quantum-well laser: Calibrated scanning spreading resistance microscopy and scanning capacitance microscopy

Abstract

We report results of a scanning spreading resistance microscopy ͑SSRM͒ and scanning capacitance microscopy ͑SCM͒ study of the distribution of charge carriers inside multi-quantum-well ͑MQW͒ buried heterostructure ͑BH͒ lasers. We demonstrate that individual quantum-well-barrier layers can be resolved using high-resolution SSRM. Calibrated SSRM and SCM measurements were performed on the MQW BH laser structure, by utilizing known InP dopant staircase samples to calibrate the instrumentation. Doping concentrations derived from SSRM and SCM measurements were compared with the nominal values of both p-and n-doped regions in the MQW BH lasers. For n-type materials, the accuracy was bias dependent with SSRM, while for SCM, excellent quantitative agreement between measured and nominal dopant values was obtained. The SSRM was able to measure the dopant concentration in the p-type materials with ϳ30% accuracy, but quantitative measurements could not be obtained with the SCM. Our results demonstrate the utility of combining calibrated SSRM and SCM to delineate quantitatively the transverse cross-sectional structure of complex two-dimensional devices such as MQW BH lasers, in which traditional one-dimensional probing using secondary ion mass spectroscopy provides only a partial picture of internal device structure.

Direct observation of electron overbarrier leakage in actively driven buried heterostructure multi-quantum-well lasers

“…The radius of the AFM tip is around 20 nm, and the spatial resolution of the SSRM/SDSRM measurements is expected to be on the same order of magnitude. The SDSRM measurements were performed under optimized conditions that were found from the SSRM experiments [26], under which the measured signal showed monotonic relation with local carrier density in the device under test.…”

“…The tip was scanned at 0.25-4 µm/s with forces in the range of 2-5 µN. Details about SSRM and SDSRM can be found in references [26,29] A simple analysis indicates the dc current (in SSRM measurements) or the ac current (in SDSRM measurements) is inversely proportional to the differential spreading resistance in the vicinity of the tip and thus, is proportional to the product of the local free carrier concentration (n) and the carrier mobility of the point contact. As the SPM tip scans on the transverse cross-section of a BH MQW laser, the measured current signal (dc in SSRM and ac in SDSRM) is collected and can be converted to a two-dimensional profile of the free carrier concentration inside the device.…”

“…Scanning probe microscopy (SPM)-based techniques such as scanning spreading resistance microscopy (SSRM) [19,20] and scanning capacitance microscopy [21,22] have been used for twodimensional (2D) dopant profiling in semiconductor devices in equilibrium states. The quantitative capabilities of these techniques have been demonstrated on unbiased Si-based structures [23] and InP-based structures [24][25][26]. More recently, Zavyalov and co-workers [27] reported the application of scanning capacitance microscopy on the transverse cross section of an actively-biased metal-oxide-semiconductor field-effect transistor.…”

New DFB grating structure using dopant-induced refractive index step

“…The growth initiation temperature was 625 C, the remaining layers were grown at 650 C except for the aluminium-containing layers, which were grown at 700 C to minimise oxygen incorporation. Scanning electron microscopy (SEM) and transmission electron microscopy cross-section analysis did not reveal the grating due to the high-quality etch and regrowth, thus we utilised scanning spreading resistance microscopy (SSRM), which is a cross-sectional scanning probe technique that is sensitive to dopant concentrations [15]. The SSRM measurements were performed using a commercial instrument (DI Veeco, Dimension 3100), equipped with the appropriate SSRM applications module.…”

Scanning spreading resistance microscopy of undoped CdS/ZnSSe multiple quantum well heterostructure

“…SSRM technique can be applied for technology control of different kinds of semiconductor devices [2,3]. At this moment devices based on vast variety of doped low resistivity III-V materials have been investigated with SSRM.…”