Exhibit d.18

This Security is a Global Note within the meaning of the Indenture hereinafter referred to and is registered in the name of The Depository Trust Company or a nominee thereof. This Security may not be exchanged in whole or in part for a Security registered, and no transfer of this Security in whole or in part may be registered, in the name of any Person other than The Depository Trust Company or a nominee thereof, except in the limited circumstances described in the Indenture.

Unless this certificate is presented by an authorized representative of The Depository Trust Company to the issuer or its agent for registration of transfer, exchange or payment and such certificate issued in exchange for this certificate is registered in the name of Cede & Co., or such other name as requested by an authorized representative of The Depository Trust Company, any transfer, pledge or other use hereof for value or otherwise by or to any person is wrongful, as the registered owner hereof, Cede & Co., has an interest herein.

Hercules Technology Growth Capital, Inc.

6.25% Notes due 2024

Hercules Technology Growth Capital, Inc., a corporation duly organized and existing under the laws of Maryland (herein called the “Company”, which term includes any successor Person under the Indenture hereinafter referred to), for value received, hereby promises to pay to Cede & Co., or registered assigns, the principal sum of THREE MILLION U.S. DOLLARS (U.S.$3,000,000) on July 30, 2024, and to pay interest thereon from July 14, 2014 or from the most recent Interest Payment Date to which interest has been paid or duly provided for, quarterly on January 30, April 30, July 30 and October 30 in each year, commencing July 30, 2014, at the rate of 6.25% per annum, until the principal hereof is paid or made available for payment. The interest so payable, and punctually paid or duly provided for, on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security is registered at the close of business on the Regular Record Date for such interest, which shall be January 15, April 15, July 15 and October 15 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date. Any such interest not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Security is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of Securities of this series not less than 10 days prior to such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by such exchange, all as more fully provided in said Indenture. This Security may be issued as part of a series.

Payment of the principal of (and premium, if any, on) and any such interest on this Security will be made at the office of the Trustee located at 100 Wall Street, Suite 1600, New York, New York, 10005, Attention: Hercules Technology Growth Capital, Inc. (6.25% Notes Due 2024) and at such other address as designated by the Trustee, in such coin or currency of the United States of America as at the time of payment is legal tender for payment of public and private debts; provided, however, that at the option of the Company payment of interest may be made by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register; provided, further, however, that so long as this Security is registered to Cede & Co., such payment will be made by wire transfer in accordance with the procedures established by The Depository Trust Company and the Trustee.

Reference is hereby made to the further provisions of this Security set forth on the reverse hereof, which further provisions shall for all purposes have the same effect as if set forth at this place.

Unless the certificate of authentication hereon has been executed by the Trustee referred to on the reverse hereof by manual signature, this Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose.

IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed.

Dated:

Attest

This is one of the Securities of the series designated therein referred to in the within-mentioned Indenture.

Dated:

Hercules Technology Growth Capital, Inc.

6.25% Notes due 2024

This Security is one of a duly authorized issue of Senior Securities of the Company (herein called the “Securities”), issued and to be issued in one or more series under an Indenture, dated as of March 6, 2012 (herein called the “Base Indenture”, which term shall have the meaning assigned to it in such instrument), between the Company and U.S. Bank National Association, as Trustee (herein called the “Trustee”, which term includes any successor trustee under the Base Indenture), and reference is hereby made to the Base Indenture for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the Company, the Trustee, and the Holders of the Securities and of the terms upon which the Securities are, and are to be, authenticated and delivered, as amended and supplemented by the Third Supplemental Indenture relating to the Securities, dated as of July 14, 2014, by and between the Company and the Trustee (herein called the “Third Supplemental Indenture”; and together with the Base Indenture, the “Indenture”). In the event of any conflict between the Base Indenture and the Third Supplemental Indenture, the Third Supplemental Indenture shall govern and control.

This Security is one of the series designated on the face hereof, which series is initially limited in aggregate principal amount to $103,000,000. Under a Board Resolution, Officers’ Certificate pursuant to Board Resolutions or an indenture supplement, the Company may from time to time, without the consent of the Holders of Securities, issue additional Securities of this series (in any such case “Additional Securities”) having the same ranking and the same interest rate, maturity and other terms as the Securities. Any Additional Securities and the existing Securities will constitute a single series under the Indenture and all references to the relevant Securities herein shall include the Additional Securities unless the context otherwise requires. The aggregate amount of outstanding Securities represented hereby may from time to time be reduced or increased, as appropriate, to reflect exchanges and redemptions.

The Securities of this series are subject to redemption in whole or in part at any time or from time to time, at the option of the Company, on or after July 30, 2017, at a redemption price per security equal to 100% of the outstanding principal amount thereof plus accrued and unpaid interest payments otherwise payable for the then-current quarterly interest period accrued to the date fixed for redemption.

Notice of redemption shall be given in writing and mailed, first-class postage prepaid or by overnight courier guaranteeing next-day delivery, provided that so long as the Securities are registered to Cede & Co., such notice shall be given in accordance with the Trustee’s and the Depositary’s standard practices and procedures, to each Holder of the Securities to be redeemed, not less than thirty (30) nor more than sixty (60) days prior to the Redemption Date, at the Holder’s address appearing in the Security Register. All notices of redemption shall contain the information set forth in Section 11.04 of the Base Indenture.

Any exercise of the Company’s option to redeem the Securities will be done in compliance with the Indenture and the Investment Company Act, to the extent applicable.

If the Company elects to redeem only a portion of the Securities, the Trustee or, with respect to Global Notes, the Depositary will determine the method for selecting the particular Securities to be redeemed, in accordance with the Indenture and the Investment Company Act, to the extent applicable. In the event of redemption of this Security in part only, a new Security or Securities of this series and of like tenor for the unredeemed portion hereof will be issued in the name of the Holder hereof upon the cancellation hereof.

Unless the Company defaults in payment of the Redemption Price, on and after the Redemption Date, interest will cease to accrue on the Notes called for redemption.

Holders of Securities do not have the option to have the Securities repaid prior to July 30, 2024.

The Indenture contains provisions for defeasance at any time of the entire indebtedness of this Security or certain restrictive covenants and Events of Default with respect to this Security, in each case upon compliance with certain conditions set forth in the Indenture.

If an Event of Default with respect to Securities of this series shall occur and be continuing, the principal of the Securities of this series may be declared due and payable in the manner and with the effect provided in the Indenture.

The Indenture permits, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series to be affected under the Indenture at any time by the Company and the Trustee with the consent of the Holders of not less than a majority in principal amount of the Securities at the time Outstanding of each series to be affected. The Indenture also contains provisions permitting the Holders of specified percentages in principal amount of the Securities of each series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and upon all future Holders of this Security and of any Security issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security.

As provided in and subject to the provisions of the Indenture, the Holder of this Security shall not have the right to institute any proceeding with respect to the Indenture or for the appointment of a receiver or trustee or for any other remedy thereunder, unless such Holder shall have previously given the Trustee written notice of a continuing Event of Default with respect to the Securities of this series, the Holders of not less than 25% in principal amount of the Securities of this series at the time Outstanding shall have made written request to the Trustee to institute proceedings in respect of such Event of Default as Trustee and offered the Trustee indemnity reasonably satisfactory to the Trustee against the costs, expenses and liabilities to be incurred in compliance with such request, and the Trustee shall not have received from the Holders of a majority in principal amount of Securities of this series at the time Outstanding a direction inconsistent with such request, and shall have failed to institute any such proceeding, for sixty (60) days after receipt of such notice, request and offer of indemnity. The foregoing

shall not apply to any suit instituted by the Holder of this Security for the enforcement of any payment of principal hereof or any premium or interest hereon on or after the respective due dates expressed herein.

No reference herein to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay the principal of and any premium and interest on this Security at the times, place and rate, and in the coin or currency, herein prescribed.

As provided in the Indenture and subject to certain limitations therein set forth, the transfer of this Security is registrable in the Security Register, upon surrender of this Security for registration of transfer at the office or agency of the Company in any place where the principal of and any premium and interest on this Security are payable, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or his attorney duly authorized in writing, and thereupon one or more new Securities of this series and of like tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees.

The Securities of this series are issuable only in registered form without coupons in denominations of $25 and any integral multiples of $25 in excess thereof. As provided in the Indenture and subject to certain limitations therein set forth, Securities of this series are exchangeable for a like aggregate principal amount of Securities of this series and of like tenor of a different authorized denomination, as requested by the Holder surrendering the same.

No service charge shall be made for any such registration of transfer or exchange, but the Company or Trustee may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith.

Prior to due presentment of this Security for registration of transfer, the Company, the Trustee and any agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not this Security be overdue, and neither the Company, the Trustee nor any such agent shall be affected by notice to the contrary.

All terms used in this Security which are defined in the Indenture shall have the meanings assigned to them in the Indenture.

The Indenture and this Security shall be governed by and construed in accordance with the laws of the State of New York, without regard to principles of conflicts of laws.