Hall bar device processing on patterned substrates using optical lithography P. Elia Âs Ï * , S. Haseno Èhrl, J. Fedor, V. Cambel Institute of Electrical Engineering, Slovak Academy of Sciences, Du Âbravska  9, 842 39 Bratislava, Slovak Republic Received 20 November 2001; received in revised form 19 April 2002; accepted 16 May 2002 Abstract Anon-planarInP-basedHallbardevicewasmanufacturedusingdeepwetetching,epitaxialovergrowthandnon-planardeviceprocessing withopticallithography.TheHallbarwasde®nedinann-dopedInPlayerat(110)and(1  10)quasifacetsofmesaridgepatternsovergrown usingorganometallicvapourphaseepitaxy(OMVPE).Initialgalvanomagneticmeasurementswerecarriedouttotestthedevice,whichwas designed to assist in the characterisation of non-planar epitaxial layers as well as in the development of a vector magnetic ®eld sensor. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Micromaching; Non-planar OMVPE; Lithography; InP; Non-planar Hall-effect sensor 1. Introduction Non-planar epitaxial overgrowth of III±V semiconductor materials on patterned substrates has been intensively studied for a long time. The aim is to simplify the design and technology of various electronic and photonic devices and to advance their integration, as well as to incorporate new low-dimensional structures, such as quantum wires and quantum dots [1]. The potential of non-planar epitaxy of III±V semiconductors for novel device concepts can be further extended if it is combined with micromachining. This paper reports on a non-planar InP-based Hall bar device.TheHallbarwasde®nedinsidefacetsofovergrown patterned features. The technology of the device included deep wet-etch patterning of planar InP substrates, organo- metallic vapour phase epitaxy (OMVPE) overgrowth of patterned substrates with an n-doped InP bulk layer and non-planar conventional-photolithography-based device processing. The motivation to create the non-planar InP-based Hall bar device is linked with our intention to use overgrown patterned features with speci®cally oriented side facets to makeanovelHall-effect-basedvectormagnetic®eldsensor. Tomanufacturesuchadevice,itisnecessarytocontrolside- facet growth processes including dopant incorporation to achieve desirable carrier concentration and carrier mobility. It was shown that both dopant incorporation and doping ef®ciency are functions of crystallographic orientation as well as growth conditions [2]. The present device is thus, primarilymanufacturedtoallowfortheevaluationofcarrier concentration and carrier mobility in epitaxial layers grown over side facets of patterned features using electrical and galvanomagnetic characterisation techniques. However, it canalsobeusedasanon-planarsensorofthemagnetic®eld. 2. Device technology 2.1. Patterning and overgrowth Non-planar InP wafers were prepared by the wet-etch patterning of standard semi-insulating Fe-doped (1 0 0) planar InP wafers in a solution of HCl and H 3 PO 4 through abasicmaskpatternconsistingof19stripsarrayedasshown in Fig.1a (thewaferandsquarearenottoscale).Thepattern was oriented 0.48 off the [0 0 1] crystallographic direction towards the [0  11] direction and it covered a square area of 10 mm  10 mm. A standard 2 in. (1 0 0) InP wafer contained 12 such squares. The resultant wet-etch patterns were long 15 mm-high ordinary mesa ridges whose cross- sectionalgeometryisoutlinedin Fig.1b.Theywerebounded byextremelysmooth(110)and(1  10)quasifacetsateach side and by strips of (1 0 0) surface at the top. The {1 1 0} facetsand(100)surfacesclosedanangleofapproximately Sensors and Actuators A 101 (2002) 150±155 * Corresponding author. Tel.: 421-2-5477-5826-2695; fax: 421-2-5477-5816. E-mail address: elekelia@savba.sk (P. Elia Âs Ï). 0924-4247/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0924-4247(02)00191-7