On the angular dependence of InP high electron mobility transistors for cryogenic low noise amplifiers in a magnetic field

Abstract

The InGaAs-InAlAs-InP high electron mobility transistor (InP HEMT) is the preferred active device used in a cryogenic low noise amplifier (LNA) for sensitive detection of microwave signals. We observed that an InP HEMT 0.3-14 GHz LNA at 2 K, where the in-going transistors were oriented perpendicular to a magnetic field, heavily degraded in gain and average noise temperature already up to 1.5 T. Dc measurements for InP HEMTs at 2 K revealed a strong reduction in the transistor output current as a function of static magnetic field up to 14 T. In contrast, the current reduction was insignificant when the InP HEMT was oriented parallel to the magnetic field. Given the transistor layout with large gate width/gate length ratio, the results suggest a strong geometrical magnetoresistance effect occurring in the InP HEMT. This was confirmed in the angular dependence of the transistor output current with respect to the magnetic field. Key device parameters such as transconductance and on-resistance were significantly affected at small angles and magnetic fields. The strong angular dependence of the InP HEMT output current in a magnetic field has important implications for the alignment of cryogenic LNAs in microwave detection experiments involving magnetic fields.In many sensitive detection systems, high electron mobility transistor (HEMT) low-noise amplifiers (LNAs) at cryogenic temperatures (1-10 K) are used to read out tiny microwave signals. Some of these systems rely on the presence of a strong magnetic field, e.g. in mass spectrometry 1 or detection of dark matter. 2,3 A potential application for cryogenic LNAs in a magnetic field is magnetic resonance imaging. 4 It has long been known that the sensitivity of the cryogenic LNA is affected by the presence of a magnetic field: when aligned perpendicular to the magnetic field, the noise temperature of a cryogenic AlGaAs-GaAs (GaAs) HEMT LNA was shown to be strongly degraded with increasing magnetic field. 5 However, reports on the electrical behavior in a magnetic field for the cryogenic InGaAs-InAlAs-InP (InP) HEMT LNA -the standard component used in today's most sensitive microwave receivers -have so far been absent. Compared to previous work, 5 we here report that the gain and noise properties for the cryogenic InP HEMT LNA are much more prone for degradation when exposed to a magnetic field. For the first time, we measured the InP HEMT at 2 K as a function of angular orientation with respect to the magnetic field. It is shown that the InP HEMT output current is limited by a strong geometrical magnetoresistance effect (gMR). The results suggest that even small a) Electronic mail: isabelr@chalmers.se b) Present address: Qamcom Research and Technology AB, Falkenbergsgatan 3, SE-412 85 Gothenburg, Sweden

Low-field Mobility and High-field Velocity of Charge Carriers in InGaAs/InP High-electron-mobility Transistors

“…It can also be seen from Fig. 1 (a), that the drain current decreases with the magnetic field, apparently, due to the GMR effect [13].…”

“…where q is the elementary charge and Cg = × 0 d is the gate capacitance per unit area, where d = 14 nm and ≈ 13 are the total thickness and the effective dielectric constant of the barrier and spacer layers, and 0 the dielectric constant for vacuum [13], [14], [29].…”

Low-Field Mobility and High-Field Velocity of Charge Carriers in InGaAs/InP High-Electron-Mobility Transistors

“…where q is the elementary charge and C g = ϵ×ϵ0 d is the gate capacitance per unit area, where d = 14 nm and ϵ ≈ 13 are the total thickness and the effective dielectric constant of the barrier and spacer layers, and ϵ 0 the dielectric constant for vacuum [18,33].…”

“…We deliberately selected HEMTs having a relatively large gate length with the goal to minimize quasi-ballistic transport effects by keeping the gate longer than the mean free path of the charge carriers, which one can consider as a limitation of the work [16,17]. The devices were fabricated using a conventional top-down approach, planar lithography and wet etching of an InGaAs/InP based heterostructure [18]. These type of HEMTs reveal excellent noise performance with minimum noise temperature down to 1 K [19].…”

Low-field Mobility and High-field Velocity of Charge Carriers in InGaAs/InP High-electron-mobility Transistors

“…The drain current tends to saturate in the whole range of gate voltages. The drain current also decreases with the magnetic field, due to the GMR effect [13].…”